Attorney general issues opinion saying medical marijuana cooperatives are illegal in Michigan

But not allowed under the state's medical marijuana law, Schuette said, are cooperatives where patients and caregivers jointly cultivate, store and share medical marijuana.

Schuette's opinion also noticeably leaves out patient-to-patient transfers of marijuana, which is the business model many dispensaries follow, as an acceptable practice. Schuette has said publicly he believes the law approved by voters in 2008 did not authorize dispensaries.

Ann Arbor officials are looking into what the opinion might mean for marijuana dispensaries and cultivation facilities that exist locally, but City Attorney Stephen Postema noted the attorney general's stance ultimately could be trumped by pending court decisions.

"I knew something like this was coming out, so we'll be looking at this," Postema said via phone today, adding the city still expects a major decision to come down from the Michigan Court of Appeals ruling on the legality of patient-to-patient transfers.

The Ann Arbor City Council adopted local medical marijuana regulations last week that allow up to 72 plants to be grown in a single location, but there is language in the ordinance saying it must be done in compliance with the Michigan Medical Marihuana Act.

Schuette clarified in his opinion today there are strict rules around how caregivers and patients can grow and access medical marijuana. He said the law contemplated that permitted activities, including the cultivation of marijuana plants, would occur on an individual basis.

Patients who wish to be self-sufficient, Schuette said, can grow up to 12 plants for their own personal medical use in an "enclosed, locked facility" that only they can access.

If patients specify a caregiver, Schuette said, they relinquish any right to possess and cultivate marijuana plants on their own — they must rely on the caregiver.

And caregivers must keep each patient's plants segregated and in a separate enclosed, locked facility that only they can access, Schuette said. That's defined as "a closet, room, or other enclosed area equipped with locks or other security devices that permit access only by a registered primary caregiver or registered qualifying patient."

Schuette said questions concerning commercial enterprises that sell medical marijuana — and whether government officials can conduct warrantless administrative searches of registered patients or caregivers and their properties — are under review by his office.

He noted in his opinion that marijuana remains a Schedule 1 controlled substance, meaning it has a high potential for abuse and has no accepted medical use in treatment in the United States. He also said the manufacture and delivery of marijuana by anyone remains a felony and the voter-approved medical marijuana law merely "sets forth particular circumstances under which they will not be arrested or otherwise prosecuted for their lawbreaking."

Ryan J. Stanton covers government and politics for AnnArbor.com. Reach him at ryanstanton@annarbor.com or 734-623-2529. You also can follow him on Twitter or subscribe to AnnArbor.com's e-mail newsletters.