<And please don't say anything along the lines of "international approval." I would probably be motivated into obscenity.

But you are already much too often, anyway!

An international treaty is a contract? (two parties) Perhaps between the UN and every signatory country.

Anyway, the UN has no coercive power; all it can do is denounce treaty violations for the world to see.

What do we get by signing a treaty that pretends North Korea is a civilized nation?

I'm not at all sure there is anywhere in treaties a stipulation that distinguishes the civilized aspect of a country, relative to another. That's not what the UN is for.
What matters is that we live in one world and there are many issues coming from countries, that affect other countries, no matter what their political regime is.
For instance: your so "beloved" marxists used to pollute Europe with their uncared old industrial activities. Pollution affects the world not just the country it comes from.
Maritime law must be the same all over, in order for commerce to work fairly. Pavillion law (for planes) also must be interationally recognized.
You won't prevent people who come from countries with totally different political regimes from falling in love. What happens to the children if one runs away with them to the country where human rights are not respected? When there's no treaty between those countries?

Raoul