Nukes don’t get “worse” because of physics, not because of laws. You can’t make a pocket Tsar Bomba even if there were no rules against proliferation.

Dial-a-yield nukes already provide a range of yields from tiny to massive, and this provides all the operational flexibility that is needed considering that nobody’s willing to actually launch them in anger. (And this reluctance again isn’t about laws, it’s about the military realities of what would happen across the world in the aftermath of even a single tactical detonation.)

Anti-proliferation agreements and laws only slow “rogue” states from rising to nuclear capability. The immense cost, complexity, technical difficulty, and danger already provide a sufficient cost to deter civilian development.