The 21st Century: The Question That Lies Present

How do countries that support an international order based on the rule of law stop moves by nuclear powers to subdue those around them by force?

Can lawless violence be suppressed by law?

Are there other means of suppressing violence than violent devices?

The idea of nuclear deterrence is that if nuclear violence is unlimited, violent devices must also be unlimited, and we must expect destructio.

For example, are extralegal means, such as assassinating a dictator as a means of eliminating a nuclear threat, acceptable under the rule of law?