"International Law" is a joke.
Laws are only effective when they are backed by force.
Right now, the only entity that had demonstrated any real ability to enforce "International Law" is the U.S. The EU is too busy getting lapped economically and militarily by the entire rest of the world. China is sensibly focusing on its own internal transitions and maturations. Russia is lost to us, or will be soon, for a generation or more. Central and South America still seem to be getting their post-Colonial shit together. Africa? Africa is tragically still the world's pesthole.
So it's up to the U.S. to enforce International Law. Sadly, the rest of the world can't come up with a single compelling reason why the U.S. should do so.
And no, "because if the U.S. weakens itself on purpose, the rest of us will feel better" isn't a compelling reason.
You know what would make Canada feel better? If they had a missile defense system of their own, so they didn't have to play the part of the U.S.'s Passive-Aggressive Useless Gay Uncle all the time.
(Nothing against gays or uncles; the phrase just has better flow this way.)
Canada's problem is that it wants to be considered a world player, but it doesn't have the wang or the will to actually play. (See also: Belgium.)
And a side note for all those of you who're waiting for China to step up and counterbalance the U.S.: One, dream on. Two, all regimes are flawed, but try living in each country for a year, speaking out as much as you like about their government's mistakes and misdeeds. Then tell me who you'd rather have running the world. (And for those of you holding out for an EU counterbalance: One, the combined wisdom and skill of France and Germany will make the world a better place? How? Two, bwaaahahaha!)