Forty years ago, Harvard psychology professor Lester Grinspoon, alarmed at the widespread use of marijuana, set out to write a scientific paper that would definitively prove that the drug was harming its young users. Here is what he found:

"By 1971 . . . I knew that far more harmful than any psychopharmacological property of this substance was the way we as a society were dealing with its use. While marijuana is, in fact, remarkably free of toxicity, the consequence of annually arresting 300,000 young people were not."

We'll leave it to the scientists to decide issues like toxicity, but 60 years have passed since the United States made possession of marijuana illegal and the evidence is clear. As the young sponsors of a bill that passed the New Hampshire House Tuesday articulated, the consequences of an arrest for even a minute amount of marijuana are serious and can have repercussions for decades.

People convicted of possessing marijuana face a year in jail and a lifetime criminal record that could make it difficult to get some jobs. They also lose their eligibility for federal financial aid, a ban that could make attending college difficult and more costly. The punishment, particularly when it is so often given to young people whose judgment is not yet fully formed, is greatly out of proportion with the crime.

The bill makes possession of a quarter ounce of marijuana or less a violation punishable by a $200 fine and confiscation of the drug. It does not legalize marijuana or change the penalties for larger quantities, manufacturing or sale.

At least 11 states have decriminalized the possession of a small amount of marijuana, generally one ounce or less. Oregon did so in 1973. Studies in those states suggest that marijuana usage increases only slightly or not at all. In Great Britain, in fact, after marijuana was decriminalized in 2004, usage went down - the theory being that the drug lost some of its allure for rebellious youth because of its new status.

It makes no sense to make criminals of young people prone to experiment with a drug most experts consider much safer than alcohol. That's no argument for legalizing marijuana, but it is cause to rethink the state's criminal penalties.

Driving while impaired, whether by alcohol, marijuana or some other drug, remains a problem. And if incidents increase as the result of the bill's passage, or if marijuana use by the young increases, the law can be repealed.

That's unlikely to be necessary. Gov. John Lynch has already threatened to veto the bill. And he probably won't even have to. Taking his lead, Senate Democrats have already indicated they're likely to kill it.

It takes courage for politicians to vote for a bill that gives their opponents an easy target - even a bill that could remove an obstacle between some teens and college. It's no surprise that Lynch raced to stop this debate before it got much further.