Affirmative action is enforced by bureaucratic procedures in the private and -- mostly -- the public sector. Such procedures can be notoriously difficult to undo, especially if someone benefits from them disproportionately. The purpose of these procedures is to "level the playing field" for different demographic groups. Once this happens (and how would we know if it does?) then we would face a serious problem.

Since bureaucratic procedures are difficult to undo even in the best of circumstances, then inertia will cause affirmative action to remain in effect for some time after it has served its ostensible purpose. Again, inertia alone will bring about this outcome. The lobbying of those who directly benefit will add to that inertia.

Outcome: The former in group becomes the out group.