The State can regulate its citizens. So, they could make the possession of ESA species illegal. But, they would have to define listed species. Say they made it illegal to possess an ESA listed species. How would you prove that the Chinook or steelhead in your possession is not part of an ESU? Especially if you bring that fish in from Canada, Alaska, Oregon, California, or Idaho.

The fun part would be that you could buy a listed animal on reservation (legally) but then couldn't leave the reservation with it.