Other way around. Nothing in history has ever been enforced "across the board", including the rule against developing nukes. A bunch of countries managed to develop them, others were stopped (so far). It wasn't done via "multilateralism" but rather by killing people who were doing it.

Unless your vision for AI regulation involves drone striking offices where AI researchers work, then there's no way to enforce it globally.

I'm not sure what point you're making anymore. The goalposts are floating in the sea. Yes, we could blow up facilities with advanced AI infrastructure. It wouldn't even be hard to locate.