One big difference here, however, is that the barrier to entry is lower. You can start doing meaningful AI R&D on existing hardware with _one_ clever person. The same was never true for nuclear weapons, so the pool of even potential players was pretty shallow for a long time, and therefore easier to control.

Frank Martucci will sort you out with an illegal debugger. Sure he'll go to jail for it when he's caught, but plenty of people risk that now for less.

With the current hardware, yes. But then again countries could highly restrict all decently powerful hardware and backdoor them, and you need permission from government to run matrix multiplication above few teraflops. Trying to mess with backdoor is a war crime.

A weak form of hardware restriction even happens now that Nvidia couldn't export to many countries.

It's this. This kind of coordination is exactly what he's been proposing ever since the current AI safety discussion started last year. However, he isn't high-profile enough to be reported on frequently, so people only remember and quote the "bomb data centres" example he used to highlight what that kind of coordination means in real terms.