“The basic libertarian principle is that everyone should have the right to do whatever he is doing unless he is committing an overt act of aggression OR A THREAT against someone else.”
I define “threat” as potential damage to another’s property with a probability of occurring that passes a “reasonable man” test.
(Specifically I exclude any absolute requirements for intentional malice or immediacy in my definition of threat)
See this article, by Walter Block
http://www2.units.it/etica/2008_1/BLOCKBARNETT.pdf
The higher the potential damage, the lower the probability required to constitute a threat to a reasonable man.
I think the potential damage of a nuclear bomb is sufficiently high, that even a small probability of use constitutes a threat.
(Unless of course the circumstances are set up so it is a tiny nuclear device, buried in a 5 mile thick lead box, 500 miles below the earth’s surface, etc, etc)