The effects that secondhand cigarrete smoke has on american health, and especially those of us in the military, are quite undesireable. Anyone should be able to endanger their own health however they choose, but should not be free to ruin the health of others without their consent.
On that note also, marijuana has very few, if any, health side effects for the user or those around them, mostly since it is not full of the terrible chemicals that are in cigarretes. If people choose to use marijuana responsibly, they should be able to legally do so. Government sanctions controlling distribution are fine, but it should not be illegal.