[threatofrain]

How do we meaningfully say that something is internationally illegal? Or how do we say that a nation commits crimes? There is no international legislative body. The International Criminal Court isn't respected. When the ICC is disrespected, an international police force doesn't come to enforce the court's will. And by what basis is the ICC even the legitimate court of the international?

[int_19h]

The notion that there are some "norms of civilized behavior" that go beyond states and their written laws is very old, dating back centuries and even millenia:

https://en.wikipedia.org/wiki/Jus_gentium

https://en.wikipedia.org/wiki/Hostis_humani_generis

It works in the same manner as unwritten common law does - set by custom and precedent.