The limitation to smoking, and smoking marijuana should be the same as that of other laws created sanely: you cannot perform an activity that encroaches on those rights of others defined by the Constitution. If smoking cigarettes, drinking, or smoking marijuana presents a direct health risk, or indirect (you get in vehicle and drive under influence), then you are in the wrong. Marijuana is not physically addictive, cigarettes (nicotine) are, as is alcohol.
The argument for legalization of marijuana is strong (in my opinion) largely because it has less bad effects than currently legal substances, and has been shown (in Amsterdam) to not see larger use in adults when legalized (or, in that case, where law looks askance). Incidence of use among younger folks is lower there than here, also. I won't bother citing, go look it up for yourself. I believe the same study cited lower use of addictive, more dangerous drugs in Amsterdam also. This makes sense, because if you can get a clean "high", for cheap, why bother to spend many times the money for known dangerous and illegal drugs. Sure, some do. The interest for casual, productive users is probably less, because cocaine, for example, is less convenient, risky, and questionable in content.
Sorry to side track there. To the thread, I say that copyright, trademark, and patenting, all need to be reviewed, and seriously changed.