It shouldn't. Even normal tobacco should be made illegal, it kills too many people and tears families apart.
How so?
Because it's illegal, or because the family refuses to accept someone who likes to smoke it?
Moderation is key. It has been proven to be useful in medical situations, and if you add some tax in there, it could help some economical things as well.
Obviously there should be restrictions if legalized, like tobacco and alcohol (which can be more harmful).