>It's an old argument of tech capitalists that nothing can be done because technology's advance is like a physical law of nature.

it is.

>The nuclear arms race and proliferation were largely stopped.

1. the incumbents kept their nukes, kept improving them, kept expanding their arsenals.

2. multiple other states have developed nukes after the treaty and suffered no consequences for it.

3. tens of states can develop nukes in a very short time.

if anything, nuclear is a prime example of failure to put a genie back in the bottle.

> kept improving them, kept expanding their arsenals.

They actually stopped improving them (test ban treaties) and stopped expanding their arsenals (various other treaties).