But two years after the state began licensing marijuana shops, the agency tasked with enforcing cannabis laws in California has not conducted similar stings targeting the state’s multibillion-dollar pot industry, the largest in the country.

Proposition 64, which was approved by voters in 2016 to legalize the sale and cultivation of pot, does not require the state to use sting operations to enforce the law. But proponents of the initiative promised aggressive action to keep marijuana out of the hands of minors, and experts and critics of legalization say the state is failing to use an important method to hold the industry accountable, even as stings using minors as decoys have become standard practice in other states that legalized pot.

“Decoy stings are a great indicator of how prevalent noncompliance truly is,” said Republican Assemblyman Tom Lackey of Palmdale, a retired California Highway Patrol officer. “They also help send a message that there are consequences for not following the law. California should be using every tool in the belt to go after noncompliant operations.”

Proposition 64 legalized the sale of marijuana for recreational use to people 21 and older. Medical cannabis can be purchased by Californians 18 or older with a doctor’s recommendation and a medical marijuana card.

Minors are routinely used by law enforcement to test whether pot shops sell to underage customers in Colorado, Washington and Oregon, where marijuana has also been legalized. In those states, the operations are seen as an effective deterrent to retailers who might otherwise sell pot to minors.

The operations “are a proven tool for improving compliance,” said Brian E. Smith, a spokesman for the Washington State Liquor and Cannabis Board. “The more we do, a better rate of compliance is achieved.”

In the last two years, Washington state enforcement officers have sent minors into pot shops 2,144 times, and retail clerks allegedly sold the drug to the underage buyers in 90 cases. The numbers have declined as word of the sting operations has gotten around to retailers, Smith said.

The state has adopted regulations that require retailers to turn away minors seeking to buy marijuana. But California officials say they have not mounted sting operations because they are not mandated by Proposition 64 and their hands are full trying to eliminate the large black market of pot sellers, some of whom have sold contaminated products including dangerous vaping cartridges.

Officials have focused their attention on responding to complaints received by the Bureau of Cannabis Control, which are sent to a state investigative unit within California’s Department of Consumer Affairs, bureau spokesman Alex Traverso said.

“Of those complaints, the vast majority are illegal retail and delivery complaints,” he said. “The priority is working on complaints received in areas where we have licensees who are impacted because illegal operators are cutting into their business.”

Black market sellers, who don’t pay taxes or comply with costly regulations including testing requirements, threaten the legal market by taking customers away from licensed sellers through unfair competition, officials say. Illicit sellers are also more likely to sell to underage customers.

A recent audit by the United Cannabis Business Assn. found there are about 2,835 unlicensed dispensaries and delivery services operating in California, more than three times the number of licensed businesses.

Despite the need to address black market sellers, some lawmakers say the state can and should do more to keep marijuana out of the hands of minors.

Opponents of Proposition 64 said backers of the initiative have failed to keep their promise to make sure the legalized system does not provide minors greater access to the drug.

“Teen access, use and harms related to marijuana are skyrocketing,” said Scott Chipman, vice president of Americans Against Legalizing Marijuana, a leading opponent of Proposition 64. “Minor decoy programs are one of many enforcement strategies that could be useful, especially if there is sufficient media regarding the outcomes.”

Lawmakers also say the state should be testing licensed pot shops by sending in minors under the supervision of law enforcement. The Legislature approved a bill in 2017 that allows law enforcement to recruit people younger than 21 to help perform sting operations.

Lackey said similar operations that have been mounted for years to prevent tobacco sales to minors have been a success.

In 2018, the California Department of Public Health conducted 3,652 undercover buy inspections statewide using decoy minors that found 361 illegal tobacco sales to underage buyers.

The state also conducted 5,443 sting operations last year in which minors supervised by law enforcement were sent into liquor stores, bars and restaurants to try to buy alcohol, resulting in the arrests of 739 people for illegally selling to underage buyers.

Violators face penalties including fines and suspended licenses.

Tobacco stings were cited as a possible model for marijuana enforcement in a 2015 report by a state commission led and appointed by then-Lt. Gov. Gavin Newsom, which recommended aggressive action to protect underage Californians from access to cannabis.

“Illegal sales by adults to minors should remain a public safety priority,” said the final report of Newsom’s Blue Ribbon Commission on Marijuana Policy, which provided recommendations for Proposition 64.

Citing experts, the panel added: “The tobacco model may provide some insights, where retailers are checked by having people go in to purchase, resulting in penalties if the retailer sells to the minor or if the retailer fails to secure the area immediately around their location.”

Newsom, now governor, declined to comment on whether the state should recruit minors for pot shop stings, but he has called for stepped up enforcement in recent months.

In response to a health crisis that has implicated cannabis used in electronic cigarettes as a potential cause of lung-related illness, Newsom issued an executive order in September calling for state agencies to develop a plan for increased enforcement to reduce illegal vaping by minors. The governor noted at the time that 14.7% of California high school students reported using cannabis last year.

Industry officials have been pressing the state to crack down on the black market, but recognize that there are other issues to contend with, said Lindsay Robinson, executive director of the California Cannabis Industry Assn.

“We’re obviously supportive of the industry not selling to minors,” Robinson said. “There are so many enforcement priorities to balance.”

Some backers of Proposition 64, including Assemblyman Rob Bonta (D-Alameda), who has led lawmakers in legislating on cannabis, say they support sending minors to pot shops as part of sting operations.

“As Prop. 64 is now fully implemented, it makes good sense to take proactive steps to ensure our children are properly restricted from cannabis products in licensed stores just as authorities do with tobacco and alcohol,” Bonta said.

Licensed cannabis stores have an added level of security in requirements that customers show ID before they can make a purchase, he noted.

“Still, it’s our responsibility to see that our laws are being followed,” Bonta said. “I would support efforts such as the use of decoys to verify compliance.”