Actually, there is more to worry about here than is obvious. Get a friendly international body to issue a ruling against the US and then a US government that doesn't want to enforce immigration laws simply accepts the international decision.
We have nothing to worry about with the government bending over to any foreign court or tribunal (and blocking the proposition that passed). Not going to happen.
The problem is what our government on its own will do (or fail to do) about the illegal immigration issue in general.