In California, the law (last I checked) specified Elapids, Vipers and Pit vipers as illegal; rear fangs are listed as legal with the exception of Boomslangs and Twig Snakes (by latin name; probably because of the nature of their venom).
Local laws can be more problematic. Just because any given state state allows hots does not mean your county or city does; some city laws simply state that anything venomous is prohibited.
The funny thing about California is that if you have a valid fishing license you are allowed to keep 2 of each native rattlesnake species legally! Any idiot with $25-$30 or whatever it costs now, can get one and keep rattlesnakes. IMO this is stupid because rattlers are much more dangerous than the copperheads I wish I could keep with my 20 years of (nonvenomous) snake experience. I knew a guy about 15 years ago who was keeping a northern pacific rattlesnake he caught (he only kept lizards prior to that); his stupid
thought he could hold it one day and guess what... hospital for almost a month and his hand never fully recovered.
My final 2 cents on this gray area, take it however you wish; sometimes these gray areas can be good if you want to keep something hot but the same gray area can allow the unintelligent, inexperienced general public get into trouble and ruin things for those with experience when they
up and there is an accident or tragedy. Bad press = more bans of harmless species.
My advice to ANYONE who wishes to keep something that exploits a gray area is: "you better know what the
you are doing". Also remember that if you have even one illegal specimen in your house, you will throw your entire collection into question (in the eyes of the law) if you are caught.
Reptile keepers have to tread so very carefully right now and some things are not worth the risk to the reptile community as a whole. If you want to bend or break the law, Think about how your actions could affect your fellow keepers; keeping your personal reptile dealings safe and legal means we will all have more ground to stand on.