What if the state legislature passes such a law, but it's struck down by a court (either state or federal)?

@ShankarSivarajan I don't think this edge case would come up (basically every court has agreed that restrictions on porn are not covered by the first amendment), but I'd say if it goes into effect even momentarily this question resolves yes

Right now, the most likely state appears to be Oklahoma - a state legislator recently introduced a bill to do just that (tacked on to a bill that ups charges for CSAM, of course). I've put up a market for Oklahoma specifically, as well: