(This story has been updated with comments from Charmie Gholson, communications director for the marijuana legalization campaign.)

The push to legalize marijuana in Michigan is under way, and cannabis activists are planning to organize Thursday night outside a University of Michigan basketball game in Ann Arbor.

"We do have language written and petitions getting ready," T.J. Rice, a local supporter of the campaign, told AnnArbor.com on Wednesday afternoon.

A grass-roots group operating under the name Repeal Today For A Safer Michigan 2012 is hoping to put the question to voters in November 2012.

The push to legalize cannabis in Michigan is under way. Ryan J. Stanton | AnnArbor.com

A draft version of the petition obtained by AnnArbor.com seeks to amend the Michigan Constitution to make pot legal for people 21 and older.

It reads as follows:

A Petition to amend the Michigan Constitution Article 1, to add: Article 1 Section 28. Repeal of Marihuana Prohibition. For persons at least 21 years of age who are not incarcerated, marihuana cultivation, possession, bodily internal possession, sale, acquisition, transfer, delivery, transportation, religious, medical or personal use, or possession or use of paraphernalia shall not be prohibited, abridged, or penalized in any manner; nor subject to civil forfeiture; provided that no person shall be allowed to operate a motor vehicle while impaired by any substance.

More than 322,600 signatures from registered voters in Michigan are needed to put that question on a statewide ballot.

Campaign volunteers are expected to meet at a medical marijuana dispensary on Ann Arbor's west side Thursday afternoon for a training session before they move across town to Crisler Arena, where U-M is taking on Penn State at 7:30 p.m.

Charmie Gholson, communications director for the campaign, said actual collection of signatures won't begin until the campaign officially kicks off in mid-January.

"We're not launching a media campaign until the 12th," said Gholson, co-owner and editor of the Midwest Cultivator and a former staff member for Law Enforcement Against Prohibition. "All we're doing is organizing volunteers. We're getting volunteers to sign up and say that they'd be willing to help the campaign."

The group also is recruiting volunteers through a website. The group plans to collect the signatures from January through early July.

According to Rice, Detroit-based criminal defense attorney Matthew Abel, who specializes in marijuana cases, is assisting the group from a legal standpoint.

Washtenaw County Clerk Larry Kestenbaum said getting a constitutional amendment on the ballot in Michigan is "much more doable" than, for example, trying to recall a governor.

The signature requirement is 2.5 times higher for a governor recall, a hurdle that proved too big of a challenge for those working to recall Gov. Rick Snyder earlier this year.

"I would expect if they have enough people together on this, they probably could get it on the ballot," Kestenbaum said of the marijuana legalization initiative.

"To do something like this, you would have to circulate it not just at the farmer's market or something like that, but probably going door to door," he said.

Kestenbaum said he hadn't thought much about whether such a proposal would pass, but he doesn't discount it considering the medical marijuana initiative won voter approval in 2008.

"I think this is going to be very interesting," he said. "I'm intrigued."

The legalization of medical marijuana in Michigan has been the subject of intense debate over the past few years as dispensaries have sprouted throughout the state. That includes several dispensaries in Ann Arbor, which caused city officials to spend considerable time crafting local medical marijuana ordinances.

But the future of dispensaries remains hazy.

Michigan Attorney General Bill Schuette, who has issued formal opinions restricting medical marijuana and backed efforts to close dispensaries this year, has said he believes the state's medical marijuana law has been hijacked by people who want to legalize the drug.

But supporters of legalization argue the current prohibition on marijuana has caused more problems than it's solved, including making it easier for minors to obtain the drug.

"We are a coalition of Michigan parents, teachers, attorneys, physicians, health professionals, former law enforcers and many others with a wide range of backgrounds and beliefs," the Safer Michigan site reads. "We believe police should stop enforcing marijuana prohibition and instead refocus their priorities to arrest violent criminals and other real threats to public safety."

Gholson said it wasn't the group's intention to announce the campaign yet, but now that the news is out, she's expecting some opposition, including from Schuette.

"We're going to have some big guns pointed at us," she said.

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 email newsletters.