My counter-argument to norms being the main deterrent is simple. It’s never going to get easier to hide an Oak Ridge in your rogue state. The industrial scale of uranium enrichment has a fundamental limit, no matter how you do it.

You have to process massive piles of mass into a very small fraction. And you have to collect all those rocks. And that’s just for fission.

As long as any country with preemptive strike capability exists, and satellites exist… I just don’t see how anyone could do it.