[T]he citizens of each state are entitled to the particular territory they collectively occupy, if and only if they are also politically committed to the establishment of a global political authority realizing just reciprocal relations.
This is the thesis that Lea Ypi defends in "A Permissive Theory of Territorial Rights," European Journal of Philosophy, 2011.
She builds this thesis from a Kantian foundation.
A cornerstone of this foundation is the "principle of right" - a principle that states that each person should be given freedom to pursue his or her happiness comparable to the equal freedom of others. This principle creates a problem for the acquisition of property (and, for similar reasons, for the acquisition of territorial rights) in that, whenever a person acquires property, one reduces the freedom of others. I say that this 160 acres of land is mine. I put a cabin on it and plow and plant the fields. In declaring that it is mine, I declare that all others must stay off. I maintain a liberty to use this land as I wish, but I deny the equal liberty to others.
This might not be the case if others had as much and as good a land to declare their own. However, there are two problems with this. The first is that this has not been the case for a long time - and perhaps never if you look at the effects that our current territorial claims have on future generations. The second problem is related to the declaration given above. It means that my ownership of this property is contingent on my support for some sort of regime that is responsible for maintaining and defend the rights of people generally to own and control property. I may exclude you from my property only insofar as I am willing to support institutions that would also keep me off of your property.
For ease of illustration, I have picked the identical rights to exclusive use of one's own property by agreeing to equally respect the rights of others to their property. However, Ypi does not make such a specific claim. She argues that this requires agreement to an institution - a "rule of all" - governing the range of rights and responsibilities concerning property.
In this way, the unilateralism of initial acquisition and the arbitrary use of exclusionary force is mitigated by the commitment to make our will consistent with others’ will through collective rules of property arbitration and enforcement.
This Kantian requirement to enter into a political organization that determines the equal property rights of all individuals means ALL individuals - not just those within a certain territorial boundary. This means that one's right to property is conditional not only to agreeing to enter into a political union with others in one's state, but to enter into a like political union that respects the equal political rights of those within other countries - a global, cosmopolitan political union.
Another route that goes in the direction of a similar conclusion is that, in the same way that individuals have a right to property only insofar as they agree to enter into a political union that establishes the equal property rights of all others in one's country, countries have a right to territorial sovereignty only insofar as they are willing to participate in a super-national political union that aims to respect the equal political sovereignty of all countries.
Ypi is not clear which of these she would favor. In the realm of theory, she talks about the relationships among individuals - that an individual has an obligation to join a community that resolves disputes of rights among all others. In the realm of practice she talks about an association of states - not of persons.
Consider that the territory of the United States requires entering into some type of agreement with other nations that respects the territorial sovereignty of countries generally, which respects not only the territorial sovereignty of the United States but that of every other country. If we are not willing to enter into such an institution, then the lack of recognition of sovereign rights applies equally to all countries - including the United States. Either there is an institution for recognizing the sovereignty of nations generally that applies to all countries including the United States, in which case its sovereignty is institutionally recognized - or there is not.
Ypi does not provide an account of what this global political association would look like. However, she provides a list of what they might do. This includes (1) negotiating boundary disputes, (2) refugees and migrations, (3) natural resource management, and (4) resolving the effects of climate change and similar cross-border effects of human actions.
One thing she does rule out - or, at least, which she claims that Kant would rule out - is the use of violence against states as a way of enforcement. The article seems to imply that such things as economic sanctions and other uses of soft power would be legitimate. However, the use of violence to impose solutions on states would involve the type of unilateral decision making incompatible with the equal freedom of others. Resorting to violence for any reason other than self-defense seems to be - if not ruled out - at least highly restricted.