As far as I can read the 1977 Protocol which among other things forbids the use of nuclear weapons is not rattified by the US.

https://en.wikipedia.org/wiki/Geneva_Conventions#Contents

If you don't like that one, here are some more:

Declaration of St. Petersburg, 1868 Hague Convention, 1907 Universal Declaration of Human Rights, 1948 Geneva Conventions, 1949 The Protocols Additional to the Geneva Conventions, 1977,

See https://cnduk.org/legality-of-nuclear-weapons/

An of course, UN Security Council resolution 255 (1968) including the 1977 clarification is still supported by USA, UK, Russia which 'positive assurance' against the use of weapons against NNWS.

(Which as an aside makes Trump's recent tweet to end Iran illegal under US law and probably a war crime).

But of course, its precisely the posession of these weapons that makes all these niceties irrelevant.

Law of the jungle.

> against nnws

The real worldwide risk of nukes is direct confrontation between nuclear powers.

Let me guess - your country has nukes or is under a formal defence umbrella with one that does.

Mine doesn't have either.

These days most countries go in conflict without declaring war on another so you can diligently ignore the Geneva convention.

The threat is implicit, never stated.