For those interested in some legal history:
In 1995, the U.N General Assembly asked the following question to the International Court of Justice: “Is the threat or use of nuclear weapons in any circumstances permitted under international law?”
Some countries, including both Iran and the United States, decided to submit their views in order to help the Court reach a conclusion.
Interestingly, the United States argued that using or threatening to use nuclear weapons is not illegal under international law, while Iran strongly maintained that the threat or use of such weapons is clearly unlawful.
Here are their respective positions:
United States: “In the view of the United States, there is no general prohibition in conventional or customary international law on the threat or use of nuclear weapons . On the contrary, numerous agreements regulating the possession or use of nuclear weapons and other state practice demonstrate that their threat or use is not deemed to be generally unlawful. Moreover, nothing in the body of international humanitarian law of armed conflict indicates that nuclear weapons are prohibited per se.”
Iran: “Notwithstanding that the prohibition of threat or use of force is a fundamental principle and a preemptory norm of international law, the humanitarian international law imposes certain restrictions on the conduct of States in times of conflict, for the purpose of alleviating the sufferings of human beings in times of armed conflict….The non-existence of legally binding instruments on the prohibition of certain types of weapons does not mean that States have an absolute right to use them….It is not logical to conclude that the threat or use of nuclear weapons is permitted, when the international community has prohibited other weapons of mass destruction with much less effects on human life.”
Now, you be the judge.