Mitt Romney' s call to indict Ahmadinejad under the Geneva Conventions seems a little vague--who would prepare the indictment? what specific crimes does Romney have in mind?--but apparently there is legal recourse, and considerable evidentiary support, to eject Iran from the United Nations. Under Chapter Two, Article Six of the U.N. Charter, a
Member of the United Nations which has persistently violated the Principles contained in the present Charter may be expelled from the Organization by the General Assembly upon the recommendation of the Security Council.
It's pretty much established beyond a reasonble doubt--which is not, in any case, the standard mentioned in the Charter--that Iran has violated, and is currently violating, U.N. principles. Of course, if the United Nations was made to live up to its principles on even a semi-regular basis, we'd live in a different world.