HELENA – Montana moved a step closer Wednesday to slapping some of the nation’s strictest limitations on medical marijuana users, doctors and suppliers as lawmakers tried to get control of an industry that has ballooned since voters approved the drug’s medical use.

The bill prohibits any sale of marijuana by asking for the drug to be given to patients free of charge, on compassionate grounds. It severely limits the number of people growers can provide to, from unlimited to just three.

Doctors would be required to establish lasting relationships with patients before prescribing use, and would be put under supervision if they suggest the treatment to more than 15 patients a year.

Medical marijuana advocates say the bill would impose the largest overhaul of any medical cannabis law among the 15 states and the District of Columbia where such use was approved by voters.

Some states have restrictive laws, but none has overturned a marijuana law or tried to undo the industry as Montana lawmakers are suggesting, said Allen St. Pierre, of the National Organization for the Reform of Marijuana Laws.

“In the end, Montana will really stand out,” he said.

The bill now goes to Gov. Brian Schweitzer, who has not indicated how he would act, but has made provisions for the bill in his budget proposal.

Colorado and Arizona regulate the sale of marijuana, while others, such as Alaska, allow users to grow their own stash but let law enforcement police infractions.

California, which was the first state to approve medical use of marijuana in 1996, allows patients to obtain the drug as relief for far-ranging illnesses such as anxiety, asthma and insomnia. It has served as cautionary tale for other states where lawmakers say it should be reserved for more specific and serious conditions.

Montana’s law would add restrictions to “chronic pain,” an illness that has been criticized as being vague and which has allowed recreational users to become registered patients. Applicants who claim to have chronic pain would have to present objective proof, such as an X-ray, or a second doctor’s opinion confirming that person’s condition.

The overhaul comes as Montana nears 30,000 medical marijuana users in a state with fewer than a million residents. Many patients are supplied by large-scale grow operations with store-fronts, and some were registered en mass via traveling cannabis caravans, where doctors prescribed the drug to hundreds of patients after brief screenings.

The state’s voters approved medical pot use in 2004, and the industry has grown nearly tenfold since 2009, when the U.S. Attorney General’s office indicated they would not prosecute users complying with state law.

Critics say the boom has led to abuse, an assertion seemingly validated by a number of recent federal raids and seizures at grow operations around the state. U.S. Attorney General for Montana Michael Cotter issued a statement last week that the Department of Justice has a priority of prosecuting businesses that market and sell marijuana.

Montana’s law would require providers that now have confidentiality to register their locations with the state and submit to unannounced inspections by law enforcement.

Montana’s Republican lawmakers, who dominate the Legislature, sent an outright repeal of the measure to the governor, who said it didn’t follow the will of voters and vetoed it. They sent him the overhaul proposal, which attempts to navigate around the federal discontent with pot in Montana and tighten down on the industry.

Critics say the overhaul is too strict, making it difficult to find a provider and denying the drug to patients in need.

Supporters of the bill have acknowledged that, but say it’s a necessary consequence of reining in the industry.