The principle of coherence between internal and external migration: an apagogical argument for open borders?

ABSTRACT

There is a broad consensus on the legitimacy of states to control immigration. However, this belief has recently been questioned, among other reasons, due to the contradiction with current practices in emigration and internal mobility. The principle of symmetry states that any restriction on immigration should also apply to emigration; or that, to the contrary, if there is a right to emigrate, there should be a corresponding right to immigrate. The principle of coherence posits that every reason one might have for moving within a country also counts for moving between countries. This article proposes to extend the coherence principle from external to internal migration, arguing that the same reasons that justify restrictions on mobility across borders justify restrictions on mobility within borders too. Therefore, either freedom of movement is a fundamental right or the right of the political community to control mobility prevails. The interests at stake are in both cases the same, so asymmetry is not warranted. This leads us to an apagogical argument for open borders.

KEYWORDS:

• Freedom of movement
• reductio ad absurdum
• cantilever argument
• open borders
• right to exclude

Introduction

Emigration is a human right, while immigration is not. Similarly, freedom of movement within a country is a human right, while freedom of movement between countries is not. This is, in other words, what article 13 of the Universal Declaration of Human Rights (UDHR) says – and, more importantly, does not say: ‘1. Everyone has the right to freedom of movement and residence within the borders of each state. 2. Everyone has the right to leave any country, including his own, and to return to his country.’¹

This asymmetry is rarely questioned in mainstream political discourse, as it is often taken for granted that every state, in the exercise of its sovereignty, has the right to control its own borders and restrict immigration. The same democracies that go to great lengths to prevent the arrival of unwanted immigrants are the first to criticize developing countries for trying to prevent the departure of highly skilled citizens. Some authors brand this position as conceptually and morally incoherent. On the one hand, the right to emigrate becomes an empty signifier without the corresponding obligation on the part of other states to allow immigration. On the other hand, the same considerations that take us to recognize freedom of movement at the national level are valid at the international level. The solution, we are told, lies in extending current rights to emigration and freedom of movement within the country so as to include a symmetrical right to immigration and freedom of movement across countries.

This is known as the ‘principle of symmetry’ in migration and the ‘principle of coherence’ with existing mobility rights, respectively. The first calls for the symmetry between emigration and immigration, whereas the second demands coherence between internal and external mobility rights. The arguments, called symmetry and cantilever, consist in extrapolating an already recognized right to another that is not yet recognized based on the similarities between the two and the logical implications that follow from recognizing the former as a right. In particular, the right to national freedom of movement is used to ground a right to international freedom of movement, in just the same way as the right to emigration is used to ground a right to immigration.

But what would happen if we applied the principle of coherence to extend restrictions from the global to the domestic sphere? The article explores this possibility and argues that every reason one might have for controlling mobility abroad can be put forward for controlling mobility at home. This is what I will refer to as the principle of coherence between internal and external migration. This does not entail that states can constrain movement within their borders as they see fit. But if constraints on freedom of national movement are not justified, then constraints on freedom of international movement should not be justified either.

The article will proceed as follows. The second section describes the cantilever and symmetry arguments. The third section sets out the principle of coherence between internal and external migration. The fourth section explores the implications of this principle for the right to exclude, for which the main arguments against freedom of international movement are applied at the national level. The fifth section makes an apagogical (or reductio ad absurdum) argument for open borders. The last section contains the conclusion.

The cantilever and symmetry arguments

According to Miller (2016a), there are three different strategies for grounding a human right to immigrate: the direct, the instrumental, and the cantilever argument. The first argues that the right in question serves basic human interests, most importantly, unimpeded bodily locomotion. The second is an argument for the human right to immigrate as a necessary condition for the exercise of other valuable human rights which are themselves directly grounded, such as freedom of association, occupation, expression, conscience, and so on. The third, and most important to this case, is known as the cantilever argument.

The strategy of the last argument is a bit different from the rest: instead of developing a justification for the purported right, it draws on an already consolidated principle or a widely acknowledged right and argues that the former is a logical extension or corollary of the latter. The underlying idea is that if A and B share certain relevant characteristics and A is a right, then B should be a prima facie right. In this way, it tries to convey the logical, not axiological, arbitrariness that entails recognizing A (internal freedom of movement or the right to emigrate) as a human right but not B (international freedom of movement or the right to immigrate) (Arcos Ramírez 2020, 291). According to Cole (2006, 1), ‘[m]oral consistency requires that we treat two or more cases in the same way unless there is some feature that makes a relevant difference. To go against this basic moral rule is to enter a world of arbitrariness.’ This way of reasoning, known in philosophy as cantilever, is not so different from that of the child (B) who, after seeing that her sibling (A) has a candy (original right), asks her parents to buy her one (derivative right). The advantage of the cantilever argument is that it shifts the burden of proof to the ones opposing the right, who will be required to show that both cases are not comparable if they intend to justify an unequal treatment, or they will have to deny the existence of the original right altogether if they want to refute its logical implication (Carens 2013, 334, fn. 19).

In this case, freedom of international movement or the right to immigrate can be derived from two primary rights: internal freedom of movement (art. 13.1 UDHR) and the right to emigrate (art. 13.2 UDHR), respectively. Carens (2013, 239, emphasis added) resorts to the first in his defence of open borders:

If it is so important for people to have the right to move freely within a state, isn’t it equally important for them to have the right to move across state borders? Every reason why one might want to move within a state may also be a reason for moving between states. One might want a job; one might fall in love with someone from another country; one might belong to a religion that has few adherents in one’s native state and many in another; one might wish to pursue cultural opportunities that are only available in another land. The radical disjuncture that treats freedom of movement within the state as a human right while granting states discretionary control over freedom of movement across state borders makes no moral sense. We should extend the existing human right of [internal] free movement. We should recognize the freedom to migrate, to travel, and to reside wherever one chooses, as a human right.

Other authors proceed in the second way, departing from the human right to emigrate to arrive at a symmetrical right to immigrate. For example, Cole (2000, 46) regards liberal asymmetry – whereby the state can restrict immigration, but not emigration – ‘not merely [as] ethically, but also conceptually, incoherent.’ In the same vein, Dummett (1992, 173) states that ‘[l]ogically, it is an absurdity to assert a right of emigration without a complementary right of immigration unless there exist in fact (as in the mid-nineteenth century) a number of states which permit free entry.’ In a world where every habitable land belongs to one state or another, crossing a border to leave one state means entering the territory of another. Hence, the very act of emigration brings with it that of immigration. To deny this, the argument goes, would be a legal nonsense, because when a right is granted the obligation not to prevent its exercise is also acquired (Velasco 2016, 205).

The latter strategy has come to be known as the symmetry argument, and it is usually treated as a distinct argument. The symmetry argument is characterized by some not as a cantilever but as an instrumental argument, in the sense that the right to immigrate is a necessary means to realize the human right to emigrate. Although it is certainly true that people need to be able to enter another country in order to exit their own, they need not have a human right to immigrate in order to exercise their human right to emigrate.² As Miller (2016a, 15, emphasis added) aptly notes, ‘[t]he right to leave one’s present country of residence can be satisfied so long as there is at least one other place that one is not prevented from entering.’ My reason for subsuming the symmetry argument under the cantilever argument is that they follow the same logic: they ‘avoid delving into the grounds on which the right is claimed, and instead focus on the alleged absurdity of recognizing A as a right without at the same time recognizing B’ (Miller 2016a, 16). Just as proponents of the cantilever argument do not attempt to establish the moral foundations of the right to internal freedom of movement, proponents of the symmetry argument do not say that the right to enter protects the same concrete interests as the right to exit; they merely contend that it is absurd to recognize the latter as a human right all the while preventing the former.

It is very important to distinguish abstract or hypothetical from concrete interests for the purposes of distinguishing the cantilever from the direct argument. By way of example, let us suppose that the right to internal freedom of movement serves only to protect the interest people have in roaming free. This is a concrete interest, albeit quite a vague one. If one were to defend the right to freedom of international movement on the grounds that it protects the same interests as the right to internal freedom of movement, this would no longer be a cantilever argument, but a direct one. Why? Because it would be implicitly acknowledging that the right in question serves basic human interests, namely, the interest in roaming free. Consequently, it would no longer be a logical argument, but an axiological one. This is why the cantilever argument ‘remains a distinct strategy provided «arbitrariness» is not cashed out in terms of the [concrete] same grounds applying in both domains, in which case it reduces to the direct strategy’ (Miller 2016a, 16).

This is why Carens, despite considering the interests at stake in national and international mobility to be the same, does not specify what these concrete interests are. He ‘mention[s] specific reasons why people might want to move only as hypothetical examples’ (Carens 2013, 239). This allows him to defend freedom of international movement without delving into the concrete grounds on which the right is claimed, thus avoiding making a direct argument for open borders. To sum up, whereas in the cantilever argument the interests protected by the original right can take any abstract form so long as they take the same form in the derivative right, in the direct argument the interests protected by the original and derivative rights always take a specified (not necessarily specific) form.

Which strategy does the symmetry argument employ? As we have seen, it cannot be an instrumental strategy, at least not if the argument is to ground a human right to immigrate as opposed to a mere safe-conduct or admission letter into a single random country. Nor is it a direct strategy, since it explicitly avoids delving into the concrete grounds on which the right to immigrate is claimed. One could attempt to extend the rationale for the right to emigrate to the right to immigrate on the grounds that they both protect the same interests. However, it will not do to say that the right to immigrate protects the same abstract or hypothetical interests as the right to emigrate, for otherwise it would collapse into a cantilever argument. For it to be a direct argument, there needs to be a concrete interest that the right to emigrate protects that applies to the right to immigrate as well. In this vein, one could argue that both rights protect ‘the interest people have in being free to access the full range of existing life options’ (Oberman 2016, 35). The problem is that advocating any such interest will inevitably commit us to an axiological argument, which is precisely what we are trying to avoid. In conclusion, the symmetry argument is best characterized as a cantilever argument, not because it seeks to draw a parallel between the abstract or hypothetical interests protected by the original right (i.e., the right to emigrate) and those protected by the derivative right (i.e., the right to immigrate), but because it deliberately seeks to avoid delving into the concrete grounds on which any of these rights are claimed, insisting instead on the logical absurdity of recognizing the right to emigrate without at the same time recognizing the right to immigrate.

In any case, my argument does not depend on the merits or demerits of the cantilever and symmetry arguments. It is enough that the state’s interests in controlling mobility abroad and at home are tantamount. The aim of this article is precisely to show that every interest a state might have in controlling mobility abroad also counts for controlling mobility at home. Therefore, if one accepts the state’s right to exclude outsiders, one must also accept the state’s right to exclude insiders. By contrast, if one rejects the states’ right to exclude insiders, one must also reject the states’ right to exclude outsiders. As I will argue, this leads us to an apagogical (or reductio ad absurdum) argument for open borders. The advantage of this argument is that it does not presuppose any particular conception of global justice or require that people’s interests in moving to other countries are the same as their interests in moving within their own country. In this sense, it appeals to even those who believe that states have a right to exclude immigrants but take it for granted that citizens have a right to move to and settle in other parts of the country.

The principle of coherence between internal and external migration

So far, the principle of coherence has been used for the purpose of substantiating a human right to immigrate. But this same strategy could be used in the opposite direction. Thus, instead of deriving the right to immigrate from the right to emigrate (modus ponens), one could extend the application of restrictions on immigration to emigration (modus tollens).³ By the same token, instead of deriving freedom of international movement from freedom of national movement (modus ponens), one could extend the application of restrictions from the international to the national level (modus tollens), so that internal mobility was governed by the same rules as external mobility. In this section I will conceive of this last possibility in theoretical terms and see what the practical implications are in the next.

To do this, I will draw on the ‘principle of symmetry’ of Goodin (1992) and Cole (2000), as well as on the ‘general principle of justice in migration’ of Ypi (2008).⁴ The former establishes a presumption in favour of symmetry in the treatment of transborder mobility: whatever the principles regulating it, they must be applied consistently in both directions (emigration and immigration) and to any kind of object (persons, goods, and capital). According to this principle, unless there are good reasons against it (e.g., in the case of explosives, drugs, black money, or terrorists), a government should not set limits on the recruitment of foreign labour while attracting the investment of foreign capital, nor should it prevent the entry of immigrants if it does not do the same with the departure of emigrants. Accordingly, ‘if it can be shown that the state does have the right to control immigration, it must follow that it also has the right to control emigration: the two stand and fall together’ (Cole 2000, 46). The latter argues that ‘if restrictions on freedom of movement could ever be justified, such restrictions ought to take equal account of justice in immigration and justice in emigration.’ In other words, ‘if R provides a valid reason for restricting incoming freedom of movement, R also provides a valid reason for restricting outgoing freedom of movement’ (Ypi 2008, 391).

In this article, I propose to extend the principle of coherence from the international to the national arena, that is, from external to internal migration. The principle of coherence between external and internal migration states the following: if restrictions on migration between countries are justified, restrictions on migration within countries are justified as well. In other words, if R is good enough reason to control external mobility, R is good enough reason to control internal mobility. As we will see, the interests at stake are in both cases the same, so there is no reason to treat them differently. Before proceeding with the implications, let me spell out three caveats.

First, this is not an absolute principle, but it must rather be understood as a presumption. There may be occasions when asymmetry is indeed warranted, in the sense that internal freedom of movement is permitted but external freedom of movement is not, or vice versa. For example, the withdrawal of the passport from a defendant who poses a significant flight risk constitutes a legitimate case of asymmetry in mobility rights, so that she can move freely around the country, but she is prevented from leaving. Additionally, a government may ex hypothesi limit the number of refugees,⁵ but it must not limit the internal mobility of those refugees it has already admitted while allowing its citizens to roam free. These are two situations in which a state could control traffic at the border, but not inside. Conversely, the declaration of a disaster or protected natural area may lead to the suspension of the right to move in that area, but it should not affect entry and exit from the country. Lastly, traffic rules and private property rights are another example of restrictions on freedom of movement that apply only at the national level, insofar as they are subject to different state jurisdictions.

Second, this article does not take sides in the underlying debate about whether states should open their borders.⁶ As we have seen, there are good reasons in favour of the right to migrate, just as there are strong arguments for the right to exclude (see the next section). My aim is other, namely, to demonstrate that the most common arguments intended to justify restrictions on mobility across borders also apply to mobility within borders. This is not a blank check for governments to regulate mobility as they see fit, though. Any curtailment of the right to freedom of movement must respect the principles of equal treatment and non-discrimination. For instance, if a state refuses entry to members of a particular religion or ethnic group, this does not entitle it to control the internal mobility of citizens who follow that religion or belong to the same ethnic group. Quite the opposite: any discrimination in mobility rights on arbitrary grounds, whether internal or external, is inadmissible.

Third, the principle of symmetry pertains only to the central government (and, at most, to those constituencies with a high level of autonomy). This means that a neighbourhood, a municipality, or a province could not, on the basis of this principle, preclude the settlement of new residents. Although most of the arguments considered in this article account for the subnational units’ right to exclude as well (Maring 2019), there are two reasons for limiting this right to the national level. The first is to prevent the state from breaking into pieces and freedom of movement being reduced to rubble. If social cohesion is to be maintained, subnational levels of government must give up their right to exclude (unless they already enjoy a high level of autonomy, in which case their social cohesion might be said to depend on their ability to exclude outsiders). The second and most important reason is that freedom of movement is essential to meet our basic needs, such that we must be able to exercise it within a sufficiently large area in order to have access to an adequate range of options.

Whether actual states provide an adequate range of options remains a contested issue. There is such a huge difference in the size and degree of development of countries that it is hard to believe that they serve as a benchmark for adequate options. Whatever constitutes an adequate range of options, the fact remains that if subnational levels of government of a sufficiently (but not redundantly) large and developed country retain the power to unilaterally exclude citizens from other parts of the country, these people will be left with a less than adequate range of options, thus rendering their scope of freedom of movement insufficient to meet their basic human needs. Let us say that Belgium is a sufficiently (but not redundantly) large and developed country. Were Flanders to prevent access to the citizens of Brussels, these would be left with a less than adequate range of options. Restrictions on internal freedom of movement would be all the more problematic in the case of insufficiently large and developed countries, whose citizens already lack an adequate range of options. In contrast, to the extent that the United States constitutes a redundantly large and developed country, Texans may be banned from entering California without their being left with a less than adequate range of options. In short, my argument is conditional on citizens having access to an adequate range of options. This explains why most subnational levels of government as well as small and underdeveloped countries do not have a right to curtail internal mobility.⁷

Implications for the right to exclude

Internal and external migration tend to be treated separately in the literature on mobility justice, such that the first is rarely questioned and goes pretty much unnoticed, whereas the second is perceived as highly problematic, making the object of heated political and philosophical debates. The national-international mobility divide is especially troubling from a normative point of view, since both give rise to the same sort of questions (Sager 2018, 60). This will become clear when we look at the effects of internal freedom of movement on those interests that prohibitions on international freedom of movement are meant to protect.

The aim of this section is not to defend the states’ right to control their borders, but to explore the implications of this purported right for internal mobility. The central thesis is that the interests are in both cases the same, so that the reasons for restricting migration between countries also account for restricting migration within countries. To do this, I will survey the most frequent arguments in support of the right to exclude and see if they are applicable to the domestic context. On the one hand, there are concerns about (1) the preservation of national culture and identity, (2) domestic social justice, and (3) national security and public health. On the other hand, there are appeals to (4) freedom of association, (5) democratic self-government, (6) the right to avoid unwanted obligations, and (7) the relevance of state coercion. The first three arguments point to the potentially negative consequences of free movement, whereas the last four rest on deontic grounds.

The preservation of national culture and identity

The first argument for the state’s right to exclude claims that people have a legitimate interest in maintaining their ‘cultural continuity over time, so that they can see themselves as the bearers of an identifiable cultural tradition that stretches backward historically’ (Miller 2014, 370). Immigrants bring with them new values, customs, and beliefs that have the potential of transforming – some would say eroding – the public culture of the nation. Thus, if it is to retain a certain degree of control over the course of events, including how the culture evolves over time, a national community needs to retain a certain degree of control over its borders.

To begin with, one may question why it is the state that has the right to exclude if we are concerned about national cultures (Higgins 2013, 34–35). A more consistent application of this argument would require that states devolve their power over admissions to national communities. Even so, one might still wonder why national cultures are the only ones worthy of protection. Many municipalities and subcultures have a distinct identity whose residents or members have a special interest in preserving. Does this entitle them to exclude anyone who does not share that particular identity? To this, it may be objected that only national cultures are robust enough to qualify for protection.⁸ This requires, as Cole (2000, 90) and Pevnick (2011, 141) note, a ‘thick’ understanding of national culture, constituted not only by a shared commitment to democratic principles, but also by the engagement in certain cultural practices (and perhaps also by the belonging to the same ethnic group). The problem with this account is that not every member of a nation meets such demanding criteria. For example, Romanies in Europe constitute a separate ethnic group with their own cultural practices. This would entail that cultural and ethnic minorities (or, for that matter, any citizen who does not abide by democratic principles) might be prevented from entering or required to leave the national territory.

Setting these difficulties aside, there is a more fundamental challenge to this argument. It seems to assume (1) that cultural changes are only exogenous and (2) that people have a right to avert cultural changes.⁹ The first assumption is clearly false. For example, the exodus from the countryside to the city over the past century brought about profound changes in the economic, political, and social structure of Spain, to the point of altering the linguistic composition of the Basque Country and Catalonia. Could the local authorities of the time have forbidden internal displacement to protect cultural minorities and preserve the rural livelihood? Judging by the second assumption, it seems so. The following passage from Tamir (1993, 151) is highly illustrative in this regard:

Ensuring the ability of all nations to implement their right to national self-determination would then lead to a world in which traditional nation-states wither away, surrendering their power to make economic, strategic, and ecological decisions to regional organizations and their power to structure cultural policies to local national communities.

Given that immigration usually affects ‘their power to structure cultural policies’, local national communities should have the right to control their borders. One might reply that strategic decisions such as this should fall on regional organizations, but this leaves the core of my argument intact. What matters is not who makes the decision, but that the decision be made. If the cultural continuity of a nation were in jeopardy due to a large influx of culturally dissimilar immigrants, the regional organization would then be entitled to act. This applies to both internal and external migration: to the extent that the prospective migrants pose a threat to the cultural continuity of the nation, they may be denied admission. In fact, there is every reason to think that in a world like the one envisioned by Tamir, where national communities took centre stage, cultural differences would be likely to intensify, and so would internal barriers to free movement.

We do not need to evoke tall tales. Big cities are experiencing major disruptions today. They have become attraction poles for many nationals, immigrants, and tourists. Some of their former residents have been expelled to the outskirts as a result of housing shortages, high rental prices, and touristification. Others have seen their neighbourhoods turned into a ‘melting pot’. Added to this is the problem of depopulation in rural areas. If internal freedom of movement is presumably driving these changes, the argument goes, it may be necessary to curtail it in order to avoid such undesirable outcomes.

Domestic social justice

The second argument takes various forms, but all of them point to the negative impact of immigration on the most disadvantaged compatriots.¹⁰ Here I will focus on two major concerns: the effects on the welfare state and the labour market. According to the first, a country with generous social welfare benefits would attract a large number of immigrants, which could jeopardize the viability of the system itself (Borjas 1995, chap. 6). The second hypothesis holds that foreign labour competes with domestic labour and devalues wages. This harms less qualified workers and benefits employers and better-off citizens the most (Cafaro 2015, chap. 4). The underlying worry in both cases is that open borders would undermine domestic social justice (Macedo 2018).

Even though the empirical evidence is inconclusive,¹¹ let us assume that the hypothesis turns out to be true, and that freedom of movement is regressive in redistributive terms. Note, however, that the same can be said about internal mobility. Large cities tend to concentrate greater opportunities and attract high-skilled workers from the rural and less industrialized parts of the country. Most countries are not immune to this trend. For example, the so-called ‘empty’ Spain is losing population along with public and private investment, thus exacerbating interterritorial inequalities. In this sense, internal mobility can have just as negative consequences for social justice as external mobility. What is more, according to Borjas (1995, 115–118), the so-called ‘welfare magnet’ effect does not play a determining role in the decision to migrate, but it does bear on the choice of residence within the country, resulting in the geographical clustering of immigrants in those regions that offer greater benefits. Therefore, rather than prohibiting their entry into the country altogether, it would make more sense to prevent their settlement in certain parts of the country.

National security and public health

The third argument is perhaps the least controversial when it comes to limiting freedom of international movement. Even the staunchest advocates of this right tend to acknowledge that, should it compromise other fundamental rights and freedoms, its restriction would be justified (Carens 1992, 25; Hidalgo 2019, 57; Oberman 2016, 33). States claim to promote the general interest of their citizens, which includes protecting national security and safeguarding public health. However, the distinctive feature of this kind of threats, as the COVID-19 pandemic has shown, is that they span across borders. Any border control is rendered useless if it does not come with additional constraints on internal mobility.

The same goes for terrorist attacks. Even a zero-immigration policy would be of dubious effectiveness in its prevention, since many terrorists are nationals, naturalized citizens or permanent residents of the country, become radicalized after their arrival, come with a non-immigrant visa, or enter clandestinely (Bergen and Sterman 2021). In a recent survey article, Helbling and Meierrieks (2022, 992) find ‘little evidence that stricter migration policies actually result in less terrorism. Rather, certain policies that alienate the migrant population appear to incite terrorism.’ ‘In the end, if we really want to deflate terrorism’s impact we will need particularly to control ourselves’ (Mueller 2006, 143).

Freedom of association

The fourth argument has been developed most notably by Christopher H. Wellman in three simple steps: ‘(1) legitimate states are entitled to political self-determination, (2) freedom of association is an integral component of self-determination, and (3) freedom of association entitles one to not associate with others’ (Wellman and Cole 2011, 13). From these premises he concludes that states have the right to exclude (or not to associate with) outsiders. Let us assume that both the premises and the conclusion are correct. The question remains whether only states have a right to self-determination and therefore to control immigration, and whether this right applies inside as well (van der Vossen 2015, 277). The author himself provides the answer to this question. In a previous work, he claims that any group large enough to adequately perform the requisite functions of a state has the right to self-determination and secession (Wellman 1995).

In this case, it would not be the national government, but subnational governments which, in the exercise of their right to self-determination, could restrict immigration from other parts of the country.¹² This detail does not alter in the least the main thesis of the article, namely, that any consideration that allows limiting external mobility also allows limiting internal mobility. The holder of the right changes, but the content of the right does not. In a more recent work, Wellman (2016) directly addresses the implications of his argument for internal mobility and concedes that it can be curtailed without violating human rights so long as people have access to an adequate range of opportunities within that area. As he puts it:

if my human rights would not be violated by my inability to migrate east of the Mississippi after the East seceded from the West, then why would my human rights be violated by my inability to move east of the Mississippi within the current context?. (Wellman 2016, 90)

Democratic self-government

The fifth argument has been advanced in different versions, but it can be subsumed under the concept of democratic self-government. Unlike freedom of association, the right to control immigration derives in this case from the right of the demos to govern itself, for the decision of whom to admit into the territory and citizenship is part and parcel of the process of self-determination (Song 2019, 69). To the extent that the incorporation of new members produces changes in the composition of the body politic and affects the decisions that will be made in the future, communities should be able to design their own immigration policies if they want to retain a certain degree of control over their future course (Miller 2016b, 62–63). Recalling Walzer’s (1983, 62) famous words:

Admission and exclusion are at the core of communal independence. They suggest the deepest meaning of self-determination. Without them, there could not be communities of character, historically stable, ongoing associations of men and women with some special commitment to one another and some special sense of their common life.

This argument faces several problems. For one, it is not at all clear who the holder of the right is, as there are multiple criteria to delimit the demos. Ultimately, they all rest on the exclusion of some group of people, something difficult to justify considering that the demos is unbounded in principle (Abizadeh 2008). According to democratic theory, any instance of coercion by political power should be justified to all those people over whom it is exercised. A paradigmatic case is that of the border regime, which subjects members and non-members of the political community alike to the coercive power of the state. Accordingly, any limitation on freedom of movement should be justified to the subjected parties, whether citizens or foreigners. This includes internal mobility, which could be rightly suspended as long as democratic procedures are respected.

The only way to circumvent this obstacle is by appealing to the importance of freedom of movement for the functioning of democracy. Citizens must be able to move freely around the country in order to interact with compatriots, learn about each other’s problems, and share their experiences. This fosters solidarity and empathy among different people and raises awareness about the common good. But above all, freedom of movement stems from the need to treat everyone equally and to establish checks and balances in order to forestall potential abuses by the government such as spatial segregation and the discrimination of minorities. According to Hosein (2013, 34, emphasis added), ‘the values of democracy and political equality both support freedom of intranational movement. These values do not seem to demand similarly extensive freedom of international movement.’ This is where he gets it wrong, though, given that these same values could be put forward to justify internal restrictions on movement. There is an important disanalogy between restrictions on freedom of international and freedom of intranational movement that calls into question the very idea that the values of democracy and political equality actually demand freedom of movement at the domestic level, but not at the international level. As Lenard (2015, 4) points out, when internal freedom of movement is restricted,

1) citizens have access to the environments in which these restrictions are agreed, and 2) these restrictions, within a democratic state, are subject to a commitment to equality which ensures that wherever restrictions on movement are implemented, doing so does not violate the fundamental [political] equality that underpins liberal democratic practice. These standards do not apply in the international environment.

As long as citizens have a right of democratic participation in the political process that determines the content of internal mobility constraints, their inability to move to other parts of the country need not entail wrongful discrimination or else render them vulnerable to abuse. Suffice it to say, these constraints must be uniformly applied rather than aimed at particular groups, and there must be adequate procedural safeguards in place to forestall potential abuses. If restrictions on freedom of movement are to be justified, they must be used to promote the general interest or to pursue a permissible public policy goal. But this is nothing new. Just as states cannot discriminate against potential immigrants on spurious grounds when they control mobility abroad, neither should they discriminate against actual citizens when they control mobility at home. In fact, the former is much more likely a risk than the latter, and yet we do not thereby conclude that states lack the right to exclude immigrants. Consequently, if democratic states have the right to restrict freedom of international movement despite the actual risk of discrimination against immigrants, then a fortiori they can have the right to restrict freedom of intranational movement despite the marginal risk of discrimination against citizens.

The right to avoid unwanted obligations

Blake (2013) has made a somewhat different argument in favour of the state’s right to exclude immigrants, based on the right of its citizens to be free from unwanted obligations. Immigrants impose new obligations on citizens without their consent, including that of protecting their human rights, something that citizens can in principle refuse.¹³ According to his ‘jurisdictional theory of immigration’, states are the only ones that can exercise this right, because the subnational levels of government lack effective authority over the territory and its population. In the case of federal countries and some supranational organizations, the reason is different, having to do with the shared project of creating a single political union, which requires that the federated or member states waive their right to exclude (Blake 2020, 81). This same concern has led us to limit the power of subnational governments over admission, but this does not rule out the possibility that the federal government itself wields that power on their behalf. As long as consistency in the application of measures is respected, the restriction of internal mobility by the latter need not be ‘anathema to the project of creating a single political community’ (Blake 2013, 123). As I said before, even if the holder changes, the right remains the same.

Furthermore, people constantly incur unconsented obligations, and their freedom is equally affected no matter these come from within or outside the border. In this article, Blake does not explicitly address the moral difference between the obligations imposed on us by our compatriots and those imposed on us by foreigners such that the former are more demanding and bind us to a greater extent than the latter. By calling for a justification on the part of foreigners for their decision to immigrate, but not for a justification on the part of nationals for their decision to stay in the country, Blake implicitly assumes that the obligations one has with respect to those who are born in one’s own country are morally different from the obligations one has with respect to immigrants (Kates and Pevnick 2014, 190). But this difference is precisely what his theory was meant to explain.

The relevance of state coercion

The only relevant difference between them that could justify this partiality towards compatriots is that they participate in the collectively upheld and coercively imposed system of laws embodied by the state (Blake 2001; Nagel 2005). Foreigners, for their part, are under the jurisdiction of their own state, and are only tangentially affected by others. This fact, known as the relevance of state coercion, is what presumably explains the different treatment in each case. Freedom of movement is supposed to be part of the bundle of rights that states owe to their citizens as a justification for the authority they exercise over them, a justification that is not equally owed to foreigners (Blake 2005, 235). As a result, ‘even if the interests underlying both freedoms [internal and external freedom of movement] are symmetrical, the duties that citizens of a receiving state owe to each other and the duties that they owe to noncitizens are asymmetrical’ (Yong 2017, 470). As Blake (2008, 967–968) puts it:

each case of coercion will give rise to different forms of justification, which in turn will give rise to distinct moral rights and duties. Not all coercion, after all, looks quite like the ongoing and pervasive power of a political state over its citizens. […] When individuals face the shared web of coercion constitutive of a modern political state, they acquire distinct duties to one another in virtue of this fact […] As such, it would be a mistake to regard their [non-members’] mobility rights as being in any way comparable to those of current members.¹⁴

For example, Spanish citizens are not allowed to vote in the French presidential elections, but nothing in this picture undermines their moral equality vis-à-vis their French neighbours. This is because different institutional contexts give rise to different sets of rights and duties. But are mobility rights part of the bundle of rights exclusive to citizens? To see why this is not the case, suppose that you live in a residential complex with a swimming pool and a tennis court that only residents have access to. The exclusion of outsiders from these facilities does not, on the face of it, undermine their moral equality. But suppose now that some outsider wants to buy or rent a house there. Would the community be entitled to exclude her? Unless she were given a good reason – and Blake’s does not seem to be one¹⁵—, this exclusion would undermine her moral equality. Similarly, the fact that I am not a French citizen may explain why I cannot vote in the French presidential elections at the moment, but it does not explain why I cannot enter France and become a French citizen in the future.

More importantly, the fact that those who belong to the state deserve special consideration for the coercion they are subject to does not settle the matter of why state membership is morally significant in the first place. In this sense, rather than a justification, it offers a descriptive account of state coercion which ultimately fails to demonstrate why membership is a morally relevant criterion that justifies the preferential treatment of citizens. Therefore, any restriction on mobility (internal or external) should apply to all persons regardless of their nationality. In this case a fortiori, because the degree of border coercion is the same (or greater) over foreigners as it is over citizens.

In short, the most frequently cited arguments in favour of the right of states to control their borders are not exclusive to mobility abroad and can therefore be used as a rationale for controlling mobility at home. The considerations are in both cases the same, so there is no reason to treat them differently. Ergo, rephrasing Cole (2000, 46), if it can be shown that the state has the right to control external migration, it follows that it also has the right to control internal migration, ‘the two stand and fall together.’

An apagogical argument for open borders?

Throughout the article I have tried to show that every reason that justifies the limitation of freedom of movement at the international level justifies the limitation of freedom of movement at the national level, since the same considerations apply. Migration is therefore either a fundamental right at all levels, or the interest of the community in controlling it prevails. What cannot be consistently upheld in any case is the right of a state to control external migration while at the same time refraining itself from exercising the slightest control over internal migration when the interests at stake are the same. Does this mean that there is a right to immigrate to other countries?

In order to answer this question, it may be helpful to take a closer look at the logical reasoning that has formed the backbone of my argument. Instead of assuming the right to internal freedom of movement to then affirm the existence of a right to external freedom of movement, I have assumed the absence of a right to external freedom of movement to deny the existence of a right to internal freedom of movement. The premise is in both cases the same: if there is a right to internal freedom of movement, there is a right to external freedom of movement. The only difference is that while in the first case the antecedent is assumed in order to affirm the consequent (modus ponens), in the second case the consequent is questioned in order to deny the antecedent (modus tollens). In fact, the so-called cantilever argument is nothing more than a modus ponens, according to which if P implies Q, and if P is true, then Q is also true, where P means that there is a right to internal freedom of movement and Q means that there is a right to external freedom of movement. In formal language: P → Q, P ⊢ Q. In natural language: (1) if there is a right to internal freedom of movement, there is a right to external freedom of movement; (2) there is a right to internal freedom of movement; (3) therefore, there is a right to external freedom of movement. For my argument, I have used a modus tollens, according to which if P implies Q, and Q is not true, then P is not true. In formal language: P → Q, ¬Q ⊢ ¬P. In natural language: (1) if there is a right to internal freedom of movement, there is a right to external freedom of movement; (2) there is no right to external freedom of movement; (3) therefore, there is no right to internal freedom of movement.

Hereupon it is possible to build an apagogical (or reductio ad absurdum) argument for open borders. The objective of this type of argument is to demonstrate that, if proposing a certain hypothesis entails denying a previously assumed thesis (contrast premise), to avoid a logically impossible synthesis (i.e., that the contrast premise is true and false at the same time), such hypothesis must necessarily be rejected in favour of its alternative (Rodríguez-Toubes 2012, 93). My argument rests on two premises: on the one hand, that it is not justified to prohibit internal freedom of movement and, on the other, that if it is justified to prohibit external freedom of movement, then it is justified to prohibit internal freedom of movement. By affirming that it is justified to prohibit external freedom of movement (hypothesis) we are denying, by modus tollens, that it is not justified to prohibit internal freedom of movement (contrast premise), given that if it is justified to prohibit external freedom of movement, then it is justified to prohibit internal freedom of movement (second premise). Therefore, to avoid conceding that it is justified to prohibit internal freedom of movement (contradiction), we must reject that it is justified to prohibit external freedom of movement (hypothesis), which leads us to the conclusion, by means of a reductio ad absurdum, that it is not justified to prohibit external freedom of movement. Laid out schematically:

1. It is not justified to prohibit a person from moving freely within the territory of the state in which she resides (contrast premise).

2. If it is justified to prohibit a person from moving freely between states, then it is justified to prohibit a person from moving freely within the territory of the state in which she resides (second premise).

3. It is justified to prohibit a person from moving freely between states (hypothesis to be refuted).

4. It is justified to prohibit a person from moving freely within the territory of the state in which she resides (this statement is deduced from 2 and 3 by modus tollens).

5. It is and it is not justified to prohibit a person from moving freely within the territory of the state in which she resides (this contradictory statement follows from 1 and 4).

6. It is not justified to prohibit a person from moving freely between states (this conclusion follows from statements 3-5 by reductio ad absurdum).

Stated in the formal language of propositional logic, based on the following propositions:

* p = It is justified to prohibit a person from moving freely within the territory of the state in which she resides.

* q = It is justified to prohibit a person from moving freely between states.

Table

1. ¬p	Contrast premise
2. p → q	Second premise
3. q	Hypothesis
4. p	MT (2, 3)
5. p ^ ¬p	I^ (1, 4)
¬q	I¬ (3–5) (Reductio ad absurdum)

In conclusion, according to the principle of coherence between internal and external mobility, if restrictions on external mobility are justified, so are restrictions on internal mobility. Therefore, anyone who intends to justify the former must be ready to accept the latter (e.g., Barry 1992, 284; Wellman 2016, 89–90). But, if it is not justified to prohibit a person from moving freely within the territory of the state, then it is not justified to prohibit that person from moving freely between states either. It is, in this respect, an apagogical argument for open borders, whose strength depends on whether or not the contrast premise is accepted, namely, that there is a right to internal freedom of movement.¹⁶

Conclusion

Political philosophy has long taken for granted the right of states to control immigration, as well as their obligation to permit emigration and freedom of movement within borders. Only recently has this asymmetry been called into question. The present article contributes to this debate by proposing a new approach to address the gap between internal and external mobility rights. Instead of deriving freedom of international movement from the widely accepted right to freedom of national movement (modus ponens), it has explored the possibility of extending restrictions on mobility from the international to the national realm (modus tollens). The principle of coherence between internal and external migration states that if restrictions on migration between countries are justified, restrictions on migration within countries are justified as well.

To see why, it has surveyed the most frequent arguments in support of the right to exclude outsiders, demonstrating that they also support the right to exclude insiders, for the interests at stake are in both cases the same. Absent a strong justification to the contrary, states cannot coherently restrict mobility abroad while refusing to restrict mobility at home, or vice versa. Finally, it has made an apagogical (or reductio ad absurdum) argument for open borders. If claiming that it is justified to prohibit external freedom of movement will lead us to deny that it is not justified to prohibit internal freedom of movement, one must either conclude that it is not justified to prohibit external freedom of movement or assume that it is justified to prohibit internal freedom of movement.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

¹ The International Covenant on Civil and Political Rights (ICCPR) of 1966 merely ratifies the above.

² This claim rests on an understanding of the human right to immigrate as ‘the right to migrate to any state, not just to one or a few states’ (Miller 2016a, 14).

³ Ypi (2008, 415–416) briefly considers the idea of a ‘closed borders utopia’, but she does not endorse it.

⁴ In doing so, I do not mean to endorse these authors’ views. I discuss their principles for illustrative purposes only.

⁵ Provided that there was an equitable distribution of refugees among countries and the country had already done its fair share. I say ex hypothesi because it is not clear whether such a country would then be exempt from its second- or n-order duties of justice towards unprotected refugees (see Owen 2016, 285–288).

⁶ This issue has been addressed in Niño Arnaiz (2022).

⁷ One might worry that this condition limits the scope of my argument to a few countries. However, this depends on what one takes an adequate range of options to be. The larger and more developed countries need to be in order to count as offering an adequate range of options, the smaller the number of countries that may restrict internal freedom of movement. The problem with a demanding threshold of adequacy is that the number of countries that may restrict external freedom of movement will be many times as small, since more people will be coming from countries that do not offer an adequate range of options. Thus, to the extent that countries cannot exclude people who lack an adequate range of options, this objection is self-defeating.

⁸ In this regard, Miller (1995, 27) mentions five characteristics that serve to distinguish national identity from other forms of identity: it is ‘(1) constituted by shared belief and mutual commitment, (2) extended in history, (3) active in character, (4) connected to a particular territory, and (5) marked off from other communities by its distinct public culture.’

⁹ If the assumption was instead that people have a right to avert exogenous cultural changes only, we would be left wondering whether it is possible to do so without isolating oneself completely from the outside world, including international trade and foreign media.

¹⁰ To justify the priority of compatriots, some appeal to the relevance of state coercion (Blake 2001), others appeal to the ethical character of national communities (Miller 1995), and yet others take it for granted without further explanation (Borjas 1995).

¹¹ As Kukathas (2021, 132) observes, ‘[e]vidence pointing to losses endured by immigrant-welcoming societies suggests, at worst, modest losses overall, while evidence pointing to gains suggests only modest gains.’

¹² Pevnick (2011, 62) makes the same point: ‘the associative argument does allow California, and even Los Angeles, to block movement – but only at the cost of secession.’

¹³ Of course, there may be situations where the rights of immigrants prevail over the rights of citizens, especially when the former’s human rights are not adequately protected in their country of origin (Blake 2013, 125–126).

¹⁴ The order of the last two sentences has been reversed.

¹⁵ Blake would probably tell her that, since she is not subject to the rules of the community and she does not pay community fees, she has no right to become a member. This argument, as Abizadeh (2016, 113–114) notes, is question-begging: if whether of not one is subject to the coercive power of the state depends on whether or not one has been admitted, then the fact that one is not subject to the coercive power of the state because she has not yet been admitted cannot be cited as a justification for denying her admission.

¹⁶ Another possibility would be to reject the second premise altogether, arguing that the limitations on freedom of movement are due to different reasons in each case. But if the principle of coherence between internal and external migration holds true, this would not be possible.