for San pedro and Peruvian torch its legal to grow but you would probably be better off buying a live cactus and cutting a part of it which can regrow into another cactus. As far as purchasing them, nurseries and look online, it should yield some results. If a cactus is being prepared for consumption you are dealing with a schedule 1 compound. Peyote is illegal to possess except for certain native groups in ritual ceremonies.
Believe only L. williamsii seeds are banned in teh US, maybe other lophophora as well, but no others have heard of.
Trichocereus bridgesii, Trichocereus pachanoi, Trichocereus peruvianus and Lophophora williamsii seeds from Canada Lophophora williamsii seeds are illegal in all US states however Lophophora diffusa seeds are legal in all states other then CA. Peyote seeds and plants are legal to sell, buy and grow in Canada.
