International lawyers practicing human rights and the law of armed conflict may be understood as particular kind of expert community. Building on that community's self-understanding of their craft, this paper argues that humanitarian legal experts play a role that is not only different, but diametrically inverse, to the role played by other communities of experts when interacting with power. Where experts frame issues and influence policy makers, legal experts justify. And they do so, because their expertise leaves them no other option. Using the example of the so-called "shoot-to-kill" policies, the author addresses the role of legal expertise in the war on terror, and uses it as a proxy to asses the role of international law, as such, in anti terrorist policy.