CONCORD, N.H. — As New Hampshire again considers whether to legalize medical marijuana, neighboring states offer lessons about the complexities of implementing such a law.
The New Hampshire Legislature passed three medical marijuana bills in previous years, all vetoed by former governor John Lynch. This time, Governor Maggie Hassan’s endorsement could tip the scales. Eighteen states and the District of Columbia allow people who are sick or in chronic pain to legally buy and use medical marijuana, but laws vary widely.
A key concern of law enforcement officials is whether legalization would open the door for recreational users and people looking to profit from illicit distribution.
But in neighboring Vermont and Maine, where medical marijuana has been available for years, police say that has not been their experience.
In Vermont, policing medical marijuana is ‘‘one more thing we have to deal with, but it’s not overwhelming,’’ State Police Lieutenant J.P. Sinclair said.
He said he is aware of only a half-dozen cases of patients or caregivers selling excess marijuana illegally since medical uses of it were legalized in 2004. Medical marijuana busts are not tallied separately from other marijuana crimes, he said, making it difficult to give an exact figure.
In Maine, where medical marijuana was approved in 1999, Hallowell Police Chief Eric Nason said his department sees burglaries related to prescription opiates and other drugs, but not marijuana. His department treats a dispensary in town like any other business.
But differences among marijuana laws may make comparisons with other states irrelevant, said Enfield Police Chief Richard Crate, who opposes such legalization. In Maine, for example, possession of small amounts of marijuana for non-medical reasons is only a civil infraction, so enforcement is not a high priority, Nason said.
Crate said he sympathizes with doctors and lawmakers that want to give terminally ill patients a measure of comfort, but the list of permissible conditions in the bill is too broad.
He said New Hampshire police should not be burdened with distinguishing between medical and nonmedical users and legally and illegally grown marijuana, especially since budgets for police work are already spread thin.
Also unlike Vermont and Maine, the New Hampshire bill would allow patients with out-of-state medical marijuana cards to purchase from dispensaries.
That’s bound to create challenges of its own, said Becky DeKeuster, who operates the Hallowell dispensary and three others in Maine.
‘‘There’s such a patchwork here, with 18 states plus D.C. having different laws regarding possession limits and qualifying conditions I wouldn’t be comfortable treating patients from other states,’’ she said.
The New Hampshire proposal would also require those allowed to possess the drug to carry a registration card if they have marijuana.
If they don’t, they could be fined and arrested. Caregivers and dispensary personnel would need federal background checks and could not have prior drug convictions.