I think the federal constitution supersedes state constitutions, though.
Ah - it does! I had to look it up. It’s called the Supremacy Clause (Wikipedia). It’s not uniformly applied because many states aren’t going to bother with enforcing federal laws they disagree with. (States with legal weed, for instance.) But the federal government does have the right to poke holes in state constitutions if they deem it necessary and want to.
I could see SCOTUS taking the case, ruling horribly, the rest of the federal government not taking up enforcement, but Montana lawmakers running amok with their newfound ability to step on desperate teenagers, because SCOTUS said they could.