. >> reporter: according to prominent yale law school professor stephen carter, this marks a significant moral shift in america's use of force. >> president obama, unlike his recent predecessors, has taken the position that one of the things the american military will do in the world is intervene to protect people who are being slaughtered by their own government, and that's an enormous break with america's practice. >> reporter: in previous conflicts, including the first gulf war and air strikes in the balkans, u.s. presidents argued that while humanitarian factors may have been at play, military action was in america's strategic interests. >> the argument that is being offered for libya is entirely the argument that we have no self-interest here except to protect these people who are going to be slaughtered. now i know a lot of people think, "well, there's something else going on, there's really another reason." who knows? all that could be true, but what's really interesting is that the language the white house is using is entirely the language of humanitarian intervention. >> reporte