I would imagine international law and UN treaties would be the place to look. But otherwise my answer would be “because countries that can do a thing without someone else being able to stop them will do it and that’s just how it has always worked.” One could ask the same question if the mill...

This will serve as a precedent for the next similar incident.

They are going to use Noriega as the legal precedent. That’s how the legal system is designed- they can justify anything with case law.