A natural law view of soveriegn borders

What kind of "right" does a nation have to protect the integrity of its territorial borders? Specifically, how does a territorial border express or defend or promote the sovereignty of the sovereign citizenry of a state?

The "universal destination of the goods of the earth" implies that territory itself, mere geography, establishes no right and neither possesses nor expresses any aspect of sovereignty. Borders change over time; this is not (always) an injustice, though certain historical causes may indeed be. Nor does the ultimate root of individual and social rights -- the inherent, a priori dignity of the human person -- immediately establish a territorial law or right. Whence, therefore, this territorial right?

Such a right, I would argue, is a second-order right, derived only from what is practically and historically necessary to ensure first-order rights. That is, such a right is not an end in itself, inherently necessary for the common good, comparable to, say, the right to free speech; but rather is a means to another end, only contingently necessary for the common good, comparable to, say, the right of the sovereign to levy just taxes.

In other words, such a territorial right is both contingent and a posteriori. As a posteriori, it must be mediated by the specific and historical laws (themselves required to be just laws) which territorial integrity serves: for example, the ordinary sorts of criminal laws against murder and mayhem, which protect the common good. Just enforcement of such laws requires fairly clear territorial jurisdictions be defined; and equal and impartial enforcement within those jurisdictions is an irreducible part of the "rule of law."

As contingent, such a right is further mediated by the higher-order rights of individuals on both sides of a territorial boundary. Thus, for example, under our Constitution, the right to levy taxes is mediated by the higher-order right of citizens of adjacent states to free association, such that states may not restrictively regulate trade across inter-state borders.

International boundaries are not merely lines of jurisdiction, because the authority of the sovereign does not exceed them in normal circumstances. But, I would argue, they still serve the common good (here not merely of one sovereign, but of two or more) in a similar way, and are still mediated by the necessity of defending higher-order rights first. The principle of solidarity clearly establishes the same priority of the personal, at least in general.

Thus, in my understanding, the Church teaches that the right to work, and the right to migrate, and the right of families to live and move together, all have a higher priority than the right of the sovereign to defend its territorial integrity for its own sake. The former rights derive more immediately from the inherent, a priori dignity of the human person; the latter right does not derive from that source. The former rights mediate the latter rights. Within a single sovereign, they fully trump the latter right; while between two sovereigns, the common good still demands that the former rights may not be infringed more than necessary to prevent greater harm (as through the failure to remove terrorists from an immigrant stream, for example.)

It is, therefore, an injustice to limit legitimate paths of immigration and emigration beyond what is necessary for maintaining a proper rule of law.