I don’t understand why people use international law as their reasoning for why something is wrong or right. Law and morality are only indirectly connected - so

I don’t understand why people use international law as their reasoning for why something is wrong or right. Law and morality are only indirectly connected - something can be entirely lawful yet completely immoral, or illegal yet moral. And international law isn’t like national law because there’s no world police - break international law and you get some angry open letters from legal experts, countries that don’t like what you did complain (which they would do regardless of legality), countries that do like it don’t complain. If you’re a world power there’s nothing they can do about it.