Despite the existence of a Code of Military Justice which formalizes a number of GI rights, the army is in fact a rigidly authoritarian and coercive structure. The extraordinary GI movement that developed during the Vietnam War illustrates to what extent a political movement is able to invoke rights and make use of judicial resources, and with what limitations. How can a radical antimilitary movement take advantage of legality and phrase its demands in terms of reforms ? Examining a number of GI struggles during the Vietnam War, we try to show that one should not confuse legalistic tactics and the political aims of a movement. For a radical movement recourse to the law is a double-edged weapon. This rank-and-file movement made militant use of the possibilities offered by the law in order to change their lives and in so doing they invented new forms of democracy.