Medical marijuana has been legal in the state since a ballot measure passed in 2018, but voters went a step further this November by approving a constitutional amendment legalizing the drug for anyone 21 or older. The new law makes Missouri the 21st state to allow recreational use.

The change comes with some confusion. For one thing, dispensaries can’t yet sell for recreational use. People will eventually be able to grow their own, but applications to do so won’t be taken until next month. And places such as schools and businesses can still prohibit the drug.

John Mueller, co-founder of Greenlight Dispensaries, said the company’s 15 Missouri shops are getting calls from people confused about the new law and why they can’t yet buy it from the dispensaries.

“I think everybody’s anxious and excited about adult use,” said Mueller, whose company plans to add 300 jobs at cultivation, manufacturing and dispensary locations for the expected uptick in business. “Every dollar we sell is a dollar that doesn’t go to the black market.”

Recreational users are also calling and emailing the Missouri Wild Alchemy dispensary in O’Fallon, owner Jason Crady said — “24-7.”

“There’s a lot of buzz about it,” said Crady, who is busy hiring and training staff in preparation for recreational sales.

Existing medical dispensaries will eventually be allowed to sell to recreational users, but the agency hasn’t determined when that will be. John Payne, a leader of the campaign to legalize marijuana, said recreational sales will likely begin in February.

The state is expected to issue an additional 144 dispensary licenses by early 2025.

Spokeswoman Lisa Cox of the Missouri Department of Health and Senior Services, which regulates marijuana, said personal cultivation application forms will be available Jan. 7 for people who want to grow a limited amount of their own.

Some places will continue to prohibit lighting up. Among them: the four campuses of the University of Missouri System. The system cited two federal laws — the Drug Free Schools and Communities Act and the Drug-Free Workplace Act — on Wednesday in announcing a continued prohibition of marijuana on campuses and at university-sponsored events. Student violators could face discipline up to expulsion.

Legalization is concerning for some in law enforcement who worry it will mean more impaired drivers.

Kevin Merritt, executive director of the Missouri Sheriffs’ Association, said marijuana impairment is more difficult for police to assess because there is nothing comparable to blood-alcohol tests that determine intoxication levels in people who have been drinking.

“Basically, what do they (officers) observe of the vehicle operation?” Merritt said. “What did the officer smell and observe when they got up to the car? What kind of movements, or impaired movements, did he or she see in the operation of the vehicle to make a case that the person is impaired?”

The amendment also requires expungement of criminal records for most people incarcerated or on probation for a misdemeanor marijuana offense, a process expected to be completed by mid-2023.

It’s part of a broader move toward decriminalizing low-level marijuana crimes that has gained steam in recent years. President Joe Biden announced in October that he was pardoning thousands of Americans convicted of simple possession under federal law. Kansas City and St. Louis are among jurisdictions that have stopped prosecuting misdemeanor possession.

Dispensaries in Missouri are expecting to see lots of out-of-state buyers. Missouri is bordered by eight states, only one of which — Illinois — allows recreational marijuana sales.

Payne projects that once the program is fully up and running, Missouri will see annual sales of up to $1.3 billion.

Ron Burch, 36, of the southwestern Missouri town of Joplin, already has a medical marijuana card. He knows demand will be strong for recreational pot.

“Looking forward to February, it’s going to be a mad rush to fill all the shelves for the people that are going to be pounding down the doors to buy product,” Burch said.

Larry Stiffelman, who owns a medical dispensary in the eastern Missouri town of St. Clair, said recreational sales will be vital since, due to high taxation, his business is still struggling to make a profit.

“I can tell you that the sales will probably triple or quadruple per store,” Stiffelman said. “So it’s huge as far as the volume of business.”