While a recent poll showed that more than two thirds of Massachusetts voters favor relaxing laws against marijuana, State Representative Will N. Brownsberger ’78—a drug addiction and enforcement expert who represents parts of Belmont and Cambridge—said he has grave concerns about the wisdom of a November ballot initiative that would decriminalize possession of the drug.

The initiative, championed by the Committee of Sensible Marijuana Policy, would replace criminal penalties for possession of an ounce or less of personal use marijuana with civil penalties.

While penalties for selling, growing, and trafficking marijuana would remain unchanged, possession would be punished by a combination of a fines starting at $100, community service, and drug awareness programs. Marijuana possession would also no longer be recorded in the oft-maligned Criminal Offender Record Information system.

While some academics have come out in favor of the measure, Browsnberger called it “a side show” because the “real issue is cocaine and heroin.”

“That’s what people are going to jail for, that’s what people are dying from,” Brownsberger said, adding that the ballot measure on marijuana is “not worth pursuing.”

Supporters of the initiative argue that the current criminal penalties against marijuana cause more damage to users than the drug itself does, and that the initiative will expand civil liberties while saving police money used to combat and incarcerate marijuana users.

“Decriminalize it all the way, recognize that it’s an individual liberty to enjoy activities that impose no harm on anyone else,” said Harvard Law School professor Charles R. Nesson ’60, who in the past has admitted that he often smokes marijuana before classes. “Legally, I think it’s a very good idea [to] moderate the Draconian application of drug laws.”

Earlier this year, Nesson mounted a legal challenge to Massachusetts’ drug laws, arguing that criminalizing marijuana has no “rational basis.”

Economics professor Jeffrey A. Miron, who has devoted much of his scholarship to advocating for drug legalization, voiced similar support, but said that the initiative was only “a very small step” because “the right policy is the full legalization of all drugs.”

“I would really prefer people take a more aggressive stance.” Miron said, though he acknowledged that full legalization would be politically difficult.

Miron did, however, limit his criticism to government policy, saying that “Harvard is free to make rules of conduct and to make them Ad Board-able.”

As for common criticisms that decriminalizing marijuana sends a bad message and may encourage users to try other drugs, Miron said “the fact is that it’s not that bad, so the message would be more accurate if it were legal.” He added that “the gateway drug hypothesis”—which posits that use of marijuana will lead to use of harder drugs—“has no evidence besides what people say. It’s just stupid.”

Miron wrote a report in January estimating that Massachusetts would save approximately $29.5 million in law enforcement costs annually from decriminalizing marijuana. But Brownsberger, who was once an associate director at Harvard Medical School’s Division on Addictions, said he questioned such reports because “very few people are prosecuted or put in jail for possession of marijuana alone.”

Brownsberger also voiced concerns about how the decriminalization measure would affect college campuses.

“I think it would become a very real problem in many colleges where some students choose to smoke and some students don’t want any part of it,” Brownsberger said. “The students who don’t want any part of it will be exposed involuntarily to the effect of second-hand smoke.”

—Staff writer Peter F. Zhu can be reached pzhu@fas.harvard.edu.