He should be the one to enforce it then.
If the President says 'this is what I negotiated' we should fulfill that agreement, not look for ways to get out of the agreement or legal loopholes (sure the Ukrainians agreement said one thing, but in the English version we put something less binding). I get that doing so wouldn't be billionaire behavior that we worship (how can I get the better end of the deal AND get out of whatever commitments I made).