I mean it's a pretty difficult path to take. You have to find a foreign government willing to make this treaty and take the same steps, you have to have control

I mean it's a pretty difficult path to take. You have to find a foreign government willing to make this treaty and take the same steps, you have to have control of the State department to negotiate, have to have the President sign off on the treaty, and get a 2/3rds super majority vote from the Senate. And the treaty has to be self-executing, meaning it doesn't require the nation to create additional legislation. The state's local laws would also have to directly contradict the treaty. Also, the next President could pull us out of the treaty unilaterally at any time. Sources: Introduction in https://harvardlawreview.org/2014/01/limits-on-the-treaty-power/ https://harvardlawreview.org/2014/01/limits-on-the-treaty-po... https://en.wikipedia.org/wiki/Supremacy_Clause https://en.wikipedia.org/wiki/Supremacy_Clause https://en.wikipedia.org/wiki/Commonwealth_Edison_Co._v._Montana https://en.wikipedia.org/wiki/Commonwealth_Edison_Co._v._Mon... Honestly, if the federal government wanted to usurp state's rights, there are much easier ways than this. The commerce clause gives a lot of power to Congress, and the federal government can often encourage the states to adopt legislation by making some federal funding to the states conditional on the exaction of certain regulations, though there are limits to that.