From my understanding if you are in possession of heterodon nasicus in IL and the DNR discovers it, you'll lose the snakes and can be prosecuted. I don't think an IL resident can even buy a hognose snake from Texas and legally bring it back to IL. It is also illegal to ship a western hognose snake to IL from another state. Maybe others can chime in. But whatever the law, it is taken seriously enough to keep Western Hognose snakes from being sold at any IL show I've ever been to. If captive bred hognose snakes were allowed to be sold there, then captive breeders would sell them. I think Easterns are regulated differently.
Adam