An executive order would not cut it. The president simply does not have the authority. But an Executive Agreement on the other hand might be able to. Take a look at Belmont v. US and US v. Pink. They say some astounding stuff... Like the president's foreign affairs powers do not depend of an affirmative grant by congress or even the Constitution, and that his agreements are law.. even domestically. Of course IANAL, and not that I think about it I don't think my Con-Law professor is either, but a Phd in Gov.