Let’s say we want to solve for nuclear proliferation and eliminate this manmade existential risk. What would have to be true?

Intercept? A way to cheaply reach the warhead before it is heading down to its target and disable it? Ideally immediately at launch?

Establish a registry for all rockets and deploy interception at whichever launch hasn’t been registered?

We would need to detect launches and have enough spread out interceptors. What would these look like?