The Mexican government is trying to stop Proposition 200 ---- which the American voters of Arizona chose. That to me is about as absurd as anything we've seen --- but no one dares stand up to them.
You are correct, Breyer on SCOTUS probably wouldn't, but Scalia and Thomas would.
Look who cares that the Mexican govt. is trying to overturn Prop. 200, they can't, the people who will try to overturn it would be a Clinton/Carter packed 9th circus court in San Francisco.