The UN is basically the royal family in a constitutional monarchy—sounds impressive and appears to hold the highest authority, but the actual political power exists in the hands of the constitution.
As for the UN, they would be called in when there was a crisis. But it was just for show, like how member nations such as the US didn't respect them at all.
On the other hand, the UN would also disrespect member nations that respected them too much, since those were usually third-world nations. Su