I've updated the language there a bit, but the meaning is the same.

>There's a fairly good case to be made that playing by, and being able to set, international norms is in the long term benefit of powerful countries.

Yes, but it doesn't matter. The entire concept of truly sovereign states existing is the point. The second a state wants to leave the agreement, they just stop cooperating. There is no "greater sovereign" with which you can enforce these rules, and if there is -- say, a bigger country invading a smaller country to enforce the rules -- you're once again in a state of war, and none of the rules mattered in the first place.