There are two problems that don't disappear. The first is constitutional. In 1970, Congress passed the Controlled Substances Act, which forbids the possession or sale of marijuana. What then happened was referendums simply proceeding as though the federal act had never been passed. Such referendums authorized medical marijuana. Inevitably, the feds moved in, as in California, and got a ruling to the effect that the federal law outpoints the state law.
What came then was a kind of DMZ, the feds affirming the sovereign authority of their own law, California nodding its head and simply declining to arrest transgressors. An unspoken compromise was reached: The feds agreed to subsidize a scientific investigation into the palliative properties of marijuana, and while this goes on, the voters move at their own pace in the direction of de facto legalization.
The second problem is moral, the deep conviction by Christian men and women that to take marijuana is to commit sin. Many of those who take that position also vote for liquor prohibition, and give us here and there a dry county, or would vote for prohibition if it were once again offered as a constitutional amendment. What these people need to learn is that taking marijuana and forbidding it with the leverage of jail terms are two different things. The probability is that the fundamentalists will temporize in due course, as they run out of allies among the voters, who include the 47 percent who once tried it, mostly in their youth.
Taking pot can be risky, and stoned-while-driving should never be permitted. The scientific question -- does pot harm? -- is simply unsettled. It can be said that its ingestion has negative effects, and that there are positive effects. But experience is overwhelming the discussion, and it is teaching that however ill-advised it may be to take the drug, it is less well-advised to continue to arrest 10,000 people every week for a practice or indulgence of such exiguous social consequence.