Since the issue of nukes comes up from time to time and I was just listening to the audiobook of The Ethics of Liberty here’s Rothbard’s take on the matter;
He seems pretty anti-nuke with his “disarmament becomes the highest political good that can be pursued in the modern world” statement.
So it would seem under a natural rights ethic the possesion of nuclear bombs becomes an act of aggression in its own right and perhaps counter-aggression against the possessor would be justified.
It depends on the context. Ownership of a nuclear weapon in an area where it cannot be used without aggression could be constituted as a valid threat. However, ownership of a nuke in an area where it could be used without negativly effecting others, such as in an uninhabited wilderness, or outer space, would probably be valid. The last point I find to be especially important: nukes will probably turn out to be useful tools for the exploration and exploitation of space (asteroid mining, Orion drives, etc.).
But the idea is that having a nuclear weapon and storing it in, say, a crowded city is “aiming” it at someone. There is no possible way that the device could be used without harming others. I personally think the issue will be circumvented by insurance, though (having a nuke will give you HUGE premiums).
Although an owner of nuclear weapons could be the target of exclusion in order to punish his antisocial behavior, he could not be the target of retaliationary force until he actually committed any aggression against anyone. For all we know he is doing special types of mining and demolition.
What about nukes being used as a deterrent in an anarchist society, say by insurance companies or PDAs, against a possible threat of invasion by statist neighbours? If Iraq had functioning nukes with a real delivery system, the US wouldn’t have invaded them, for example.
Again, I would say it depends on the yield. A large-yield nuke has no real military purpose; it is a weapon for destroying cities and countryside. Using a large nuke would always involve aggression in a populated area, while a tactical nuke may not. Tactical nukes can be selectivly used against targets (say, a tank column, or an aircraft carrier), while strategic nukes cannot; that is the important distinction, mentioned by Rothbard.
To get to the point: ownership of small nukes in populated areas is valid (although would probably give you very high insurance premiums, limiting ownership to PDAs and perhaps local militias), but ownership of large nukes in populated areas is not. I would say that this is a case where the natural law has to be specified by the courts (what Aquinas called the “Human Law”).