First it's necessary to place this discussion back in context. The argument in Political Theory to which I was responding concerned the question of whether immigration controls are coercive. One of the parties to the debate argued that they are coercive whilst the other suggested that they are not but merely acts of "prevention". Basically the distinction is that some acts are ones that you can be prevented from doing without it following that you have been coerced. So if I refuse someone's request to marry me I haven't coerced them but I have prevented them from carrying something out. Similarly it may be that preventing someone from coming to a country by erecting an immigration barrier does stop them from carrying out their purpose without it following that this means that they have been coerced. Now, the reason I proceeded to prescind from the specifics of the debate was because it struck me that both parties to it effectively subscribed to a view of politics that was broadly informed by the views of Robert Nozick. On those views acts of coercion require some special justification as the nature of "right" is not defined in terms of coercion but rather more loosely by reference to something understood as "autonomy" where this notion appears to have some vague connection to the Kantian term but which Kant does not use in political philosophy. In response I was suggesting that a Kantian view is quite different since, on this view, right and authorization to use coercion are intimately connected, Kant even writing at one point that they "mean one and the same thing" (Ak. 6: 232). So my decision to prescind from the detail of the argument concerning immigration controls was based on an attempt to reach a more fundamental question of political philosophy.
However Tim's reply to my earlier posting raises a question which suggests that the response I made to the debate in Political Theory concealed a problem, a problem that, effectively prevents my being able, as easily as I thought in any case, from being able to prescind from the debate over immigration controls. There are two strands to Tim's challenge. The first concerns the way the "social contract" is referred to when Kant mentions it in his discussion of Private Right. This occurs towards the conclusion of Kant's discussion of acquisition when he writes that the problem of its justification requires reference to a notion of original acquisition before going on to write: "even if it is solved through the original contract, such acquisition will always remain only provisional unless this contract extends to the entire human race" (Ak. 6: 266).
This points to the first rationale Kant gives for a connection between the social contract and cosmopolitan considerations. To it can be added a second one to which Tim also refers. This is the very beginning of the discussion of Public Right where we find:
Since the earth's surface is not unlimited but closed, the concepts of the right of a state and of a right of nations lead inevitably to the idea of a right for a state of nations (ius gentium) or cosmopolitan right (ius cosmopoliticum). So if the principle of outer freedom limited by law is lacking in any one of these three possible forms of rightful condition, the framework of all the others is unavoidably undermined and must finally collapse. (Ak. 6: 311)Kant's concluding comment here is fairly drastic but clearly indicates the importance of the connection he felt there was between the different elements of right. Cosmopolitan right and international right are here distinguished though the difference between them is not clear at this point of the text.
Tim's general point is that the will of a given state is, by reference to other states, still a specific will, the reasoning that Kant uses to suggest that the relationship between states constitutes a state of nature. In this situation the existent state appears to those not included within its boundaries simply as a power so that whilst the state needs no specific justification for coercion in regard to its citizens it does require some justification with regard to non-citizens who are not included in the will that was established when the state was set up. Further, to go back to the specifics of the question concerning immigration controls, there needs something specific to be shown concerning what it is that requires non-citizens to be limited and regulated in terms of their entry to the state, something that specifically relates to them as non-citizens concerning why they should be limited in this way.
A lot of separate issues are involved here. Firstly, Tim is quite right to bring out the problem of provisionality with regard to states prior to establishment of a cosmopolitan contract. This is the subject of the monograph of Elizabeth Ellis to which I have given some response elsewhere. It does importantly complicate questions of state of nature theory if the relationship between states is thought of as such a state of nature although it has to be added that this view of the existent state of play between nations is not held by, for example, Habermas who instead insists that the present relations involve a form of law that shows the state of nature has, to at least some extent, been superseded. From a strict Kantian point of view, however, Tim is right to draw attention to this point.
The second point is that the connection drawn between the right of the state, international right and cosmopolitan right at the beginning of the discussion of public right does not collapse the distinctions between them. Kant indicates an important relationship between them but he does not conflate them with each other. So there is some sense to right within the state, regardless of international right and cosmopolitan right although this sense is, as Ellis and Tim both correctly argue, provisional. The scope of such provisionality hence has to be worked through which I attempted in the article I wrote in response to Ellis.
However these points are not the core of the issue. The core is rather Tim's conclusion that we cannot abjure the provision of justification of coercive measures with regard to the non-citizens who wish to enter the domain of the state. Now, within the argument of the Doctrine of Right, Kant does not address this question. Kant only looks at the reasons why colonial settlement is problematic arguing for a need for specific contracts and against force. There is no specific discussion concerning what is required for those who would wish to settle within the domain of an existent state.
However surely the Kantian response is that the existent state has, by means of the constitutional measures it has set in place, defined the scope of agreed settlement within its borders? This would not merely include the need for new settlers to adhere to the laws already given but could well incorporate considerations the citizens of the state have made to the effect that they wish to decide whether to admit new citizens. This does not have to be based, as it so often is for existent states today, on grounds of ethnicity or on implied reference to considerations of "welfare". But part of the point of an established constitution is surely one of decision that the sovereign power can determine the basis of citizenship. After all, it is normal to be able to strip citizenship from someone if they perform certain acts deemed treasonous so, similarly, there could be grounds for determining whether or not anyone is allowed to begin life as a citizen. It is true that all this is, in the strict sense, provisional but no more so than any other ground of right. This doesn't prevent it from being the case that the non-citizen needs to be given justifications for why application for citizenship is turned down but the fact that there needs to be a process of such application would itself be a settled law of the land, like any law and as such the process would be in no more need of special justification than any other and in this sense I would continue to reject the view I took to be underlying the debate that took place in Political Theory.