To paraphrase Milton Friedman, more harm has been caused by the war on drugs than drugs themselves. Around 60,000 people killed in Mexico since it started its war on drugs.
Although it is poor judgement in my opinion to even smoke tobacco, people 21 or over should be able to choose for themselves as long as no one else is put in danger such as driving while under the influence. Legalize it and tax it like alcohol and tobacco, while also educating people about the dangers of it. Better than filling up our prisons as we do now.