Nuclear Information: Nuclear Weapons and Humanitarian Law

Humanitarian Law is about people and what you can and cannot do to them in war. It would be illegal to damage neutral countries, or the natural environment, or cause unnecessary suffering.

But how much is unnecessary? How serious is serious?

The trouble is that there's international law about the rights of states as well. States are like molluscs and hamsters and humans. Their main aim is to survive. Left to themselves they'll do anything to keep going - somehow.
The World Court, or International Court of Justice is in the Hague, Netherlands is the highest possible authority on international law. In 1996 the World Court said that nuclear weapons would almost certainly be against humanitarian law. Almost certainly.

But what if a state was actually threatened with total extinction?

The Court couldn't decide on that - it wasn't given enough information.
So it might be possible to use nuclear weapons (if you are an "official nuclear weapons state" - like Britain, France, USA, China, Russia).
Basically there is a give and take between Humanitarian Law and Law to protect the rights of states. A state can cause SOME more suffering, damage to neutrals, etc if its "very survival is at stake".
But one thing never alters.
Humanitarian law says that you can never use weapons which cannot tell the difference between military and civilian targets. Targeting civilians and civilian needs, such as hospitals, is out. Always. Even if a state is on the verge of destruction. Even if the generals say that they didn't mean to kill the hundreds of thousands of civilians living near a military base.

So using nuclear weapons, or threatening to use them, might be legal if:

they are very tiny

are used in the middle of a desert

or under the Arctic

to protect a state's very life

produce little long-lasting radiation

... in which case they wouldn't be much use anyway.

So what about Actual Nuclear Weapons?

It doesn't look so good for the actual nuclear weapons, at least 30,000 of them, held by just a few countries, and ready for use at a minute's notice.
Take the case of Trident, used by Britain and the USA. Trident missiles are fired from submarines. Most of them have the same explosive power as 100 thousand tons of ordinary high explosive (100 kilotons).
Just one Trident warhead is worth 8 times the Hiroshima bomb which killed 100,000 people in a few seconds in 1945. It burnt people to a crisp with a temperature higher than the sun's. It did not kill many soldiers or destroy many war factories. Most of its victims were civilians, women, young children and babies - and even the doctors who might have been able to give the survivors some help.
And then there was radiation which causes cancers and deformities for generations. People from Hiroshima are still suffering from the effects of radiation to this day.
Retaliating against Saddam Hussein, for instance, means revenge on unborn children.

In short, nuclear weapons can never be used in a way that is accordance with humanitarian law.