Well, that begs the question of whether or not the Gitmo facility is unconstitutional or illegal (literally: it's a textbook pætitio principi).
Never mind the fact that refusing to participate in legal, ethical interrogations intended to protect the lives of millions is itself a highly unethical act. That's exactly what this blanket policy prevents: it assumes that national-security interrogations can be neither legal nor ethical, when it's pretty obvious that they can be.