Should ethnonationalist wars be resolved by formally partitioning states? The answer can't be decided case by case, because two incentive problems imply that ad hoc partitions have effects that extend across cases.

First, if the implicit criterion for major power intervention in support of partition is some level of violence, this encourages violent movements seeking to mobilize cultural difference in order to claim statehood. The Wilsonian diagnosis is wrong. Perpetual civil peace cannot be had by properly sorting "true" nations into states, because nations are not born but made, partially in response to international incentives and major power policies.

Second, an international order in which major powers go around carving up lesser powers on an ad hoc basis would make all states significantly less secure. Ad hoc use of partition to solve civil wars would undermine a relatively stable implicit bargain among
the major powers in place since the 1950s - "If you don't seek to change interstate borders by force, neither will we." I argue that this norm has been valuable, functioning in some respects like an arms control agreement. It would be irresponsible to undermine it without a thought to what might replace it, as the advocates of ad hoc partition are effectively urging. If the major powers want to start redesigning "sovereign" states, they need a political and legal framework that mitigates these two incentive effects. The best feasible solutions may be:

(1) strengthening and making more precise international legal standards on human
(and perhaps group) rights;

(2) threatening to sanction states that do not observe these standards in regard to minorities, possibly including some forms of support for agents of the
oppressed group;

(3) holding to the norm of partition only by mutual consent, but providing carrots and sticks when the state in question refuses to abide by minimal standards of
nondiscrimination.