This kind of law is different than the ones he normally breaks. It requires substantial mechanisms of government to end a treaty.

Now, he could hold up finding or refuse to mobilize troops, but at least the treaty would exist beyond him. Depending on the other members’ reactions.

But even still, this just adds an extra step that won’t really matter if he wins. If they wind up with the presidency and either/both houses, all the GOP members will fall in line with whatever he wants.