If there were, who would be the all power that would make them? That would enforce them?
There are no rules of war but what the winners make after the conflict is over.
There is no morality between nation-states. God is the only judge and history is written by winners. To assume otherwise, that some "world body" of "governance" is to cede power to that organization, which only the weak will do, never the strong. If the strong associate, it is a pretense, so that they can use the organization to influence and control the weak for their own benefit - as we have done since Bretton Woods.
You can ask such questions because you really dont understand what it means to be in an existential war because you have the privilege of living within the cocoon of the USA. The one moment that feeling of safety was threatened by a relative few terrorists a world away most Americans were ready to carpet bomb 1/2 the world to eternity and gave up a ton of personal privacy and freedoms.
All of you should take the lessons of the Melian Dialogue to heart - I encourage you to
read the whole page - As relates to the current conflict in the Ukraine, study also what happened to Melos after refusing the Athenian logic.
Athenians. For ourselves, we shall not trouble you with specious pretences- either of how we have a right to our empire because we overthrew the Mede, or are now attacking you because of wrong that you have done us- and make a long speech which would not be believed; and in return we hope that you, instead of thinking to influence us by saying that you did not join the Lacedaemonians, although their colonists, or that you have done us no wrong, will aim at what is feasible, holding in view the real sentiments of us both; since you know as well as we do that right, as the world goes, is only in question between equals in power, while the strong do what they can and the weak suffer what they must.