The case is intrinsically fascinating, with a conservative President ordering a State to abide by an international tribunal’s ruling. One problem is manifest: the Constitution clearly makes Treaties the "law of the land," akin to Constitutional Amendments and thus superior to state law, Marbury v. Madison clearly leaves the final act of legal interpretation to the Supreme Court, and well-settled precedent leaves the President extensive authority to exercise discretion in the realm of international relations.
It’s not relevant for our purposes what the right answer is for any of those. What’s useful for us is that there are often legal questions no one wants answered. A good number of legal relations are carried forward in a loose state of compromise, without a clear expression of any of the legal principles or how they apply. Litigation and trial forces these questions to be answered.
Keep that in mind when someone says they’re willing to have their day in court.