Interesting question.
I did a quick search of the Caliban Penal Code and couldn't find any indication that a smoke grenade, smoke bomb, smoke flare, etc. is illegal to manufacture or own. If not specifically illegal, it must be legal even in Californistan. (I am not a lawyer; that is my personal opinion.)
Areas in which you could get yourself into trouble with one are:
- Air pollution control laws. Some localities prohibit the burning of your own leaf litter, trash, or even charcoal grills.
- PC section 623 (4) makes it a misdemeanor to "[Burn] any material which produces any smoke or gas which is harmful to any plant or animal found in any cave."
Some areas not unique to Californistan to consider:
- Smoke grenades have an obvious legitimate use as distress signals. As with aerial flares, you can get into trouble for setting them off frivolously and someone like the Coast Guard or local lifeguards respond.
- If you start a fire with one, you've committed arson.
- If someone can claim that they were injured by the smoke or got burned by one, you can be sued.
I also couldn't find anyone on the 'Net who has them in stock, but didn't look very hard. Do you have a source?
HTH