Attorney General Maura Healey detailed her opposition to legalizing marijuana on Monday while distinguishing that stance from her prior support for a voter referendum that decriminalized possession of up to one ounce of the drug.

"I supported the effort to decriminalize small amounts of marijuana a few years ago, and I appreciated the motivation behind that move and ultimately, the law," Healey told Boston Herald Radio. "What I oppose though now is full legalization of marijuana."

Healey said her opinion was informed by conversations with attorneys general from Washington and Colorado, where voters passed marijuana legalization referendums in 2012. Healey said that those law enforcement officials have not seen a drop in drug trafficking and saw people from out of state purchase "vast amounts" of the drug to traffic it.

Following successful ballot initiatives to decriminalize possession of small amounts of marijuana in 2008 and to legalize marijuana for medical purposes in 2012, Massachusetts voters may be asked to decide another ballot question in 2016 regarding the full legalization of marijuana.

Some lawmakers have filed legislation to legalize marijuana, an effort that would at the very least give elected officials some control over the process and head off a ballot drive. Bay State Repeal, which backs a ballot question, said the bill includes "excessive" taxes on the product, making it more difficult for the legal variety to compete with the black market.

Gov. Charlie Baker also opposes the legalization of marijuana.

Colorado and Washington will be watched by proponents and opponents of full legalization, and voters in Washington, D.C. and Oregon have since legalized personal marijuana use and cultivation, according to the pro-marijuana group NORML. Oregon's law goes into effect July 1.

Healey said Colorado Attorney General Cynthia Coffman told her reduced prices on the black market keep underground drug dealers in business.

"Certainly they've seen some revenues and that was part of the motivation behind this, but at the end of the day they're seeing some real problems, particularly with the illegal drug and gun trafficking, because oftentimes guns go along with the drug trafficking there," Healey said.

A Democrat who won office last November, Healey said she supports putting drug traffickers behind bars and said "we don't see" people in Massachusetts locked up simply for possession charges.

"There's a real difference between drug users and addicts and drug traffickers," Healey said. "Do I believe that we should put drug traffickers in jail or in prison? I do. I do. You see what's happening in our communities. You see what's happening with the gang and the gun violence that's attendant to the high-level drug trafficking."

Healey said "a lot of people" went to federal jails because of the War on Drugs and said she "didn't want to confuse that with what's actually happening on the ground here in Massachusetts."

The Charlestown Democrat supports additional funding for drug recovery programs. She said police she has spoken with recently found a care-free attitude among youngsters caught smoking marijuana.

"I've talked to a number of police officers recently who say they're routinely stopping kids who are smoking in the car, and sort of say, 'Yeah. So what?'" Healey said.