The Prohibition Vector: Now an extensive review of marijuana studies has concluded that while pot affects (they don't even use the word impairs) perception, it leaves no lasting brain damage. Will this have any real impact on policy, medical or otherwise? Maybe in Canada. In America, it may be the ship arriving too late. If it weren't for the Sagan-esque billions and billions of dollars flowing to the states from tobacco settlements, I think tobacco prohibition would be a real threat -- never mind decriminalizing pot. And once tobacco is illegal, the rubric under which a plant can be grown and smoked is put away.