LANSING, MI -- A group seeking to put a marijuana legalization proposal on Michigan's 2016 ballot plans to blow by an initial 180-day window for collecting signatures and continue its petition drive into the New Year.

"We didn't use paid circulators for the first month. We're going to extend it," said Jeff Hank, chairman of the Michigan Comprehensive Cannabis Law Committee, or MI Legalize.

While the activist-led ballot committee eventually hired professional signature collection and verification companies, it also relied heavily on volunteers who are spread out across the state.

Organizers are still asking volunteers to turn in signatures by December 21 -- the original end date for the petition drive -- at which point they will have a better idea where they stand, and how many signatures they may still need to collect.

"A lot of people out there don't even know the end is coming up here," Hank said Wednesday, describing the grassroots side of the organization. "We just need to get everyone aware of that. Things are still looking good. We have the financial resources to do this."

MI Legalize, one of two committees that started circulating marijuana petitions this year, wants to legalize use of the drug by anyone over the age of 21 and tax sales at 10 percent. Local governments would license manufacturing, testing and retail facilities.

The committee will have to collect at least 252,523 valid signatures by June 1 in order to make the November 2016 ballot, and state law generally gives petitioners 180 days to do so.

"The 180-day period is a floating time frame," said Fred Woodhams, a spokesman for the Michigan Secretary of State. "It is calculated from the day of filing by counting backwards 180 days. Each campaign has to decide on moving forward whether to 'lose' signatures from the front end as more signatures are collected."

In other words, nothing precludes MI Legalize from extending its petition drive, but the group risks invalidating signatures it collected closer to launch in late June.

But Michigan law also includes a little-known provision allowing petitioners to "rebut" the "stale and void" status of a signature that was made outside the 180-day window.

And Hank, who is an attorney, is challenging the established rules for doing so. When it comes to MI Legalize, he said he wants to ensure early signers are not disenfranchised.

Current policy, adopted by the state Board of Canvassers in 1986, requires a ballot committee to prove that anyone who signed a petition outside the 180-day window was registered to vote during the 180-day period.

To do so, the petitioner can produce an affidavit or certificate from the voter who signed the petition or the clerk in the city or township where that person was registered.

That's an "extraordinary burden" that doesn't make sense, Hank wrote in a recent letter to the Bureau of Elections and Board of Canvassers. "The logical burden of locating potential tens or hundreds of thousands of people to sign an affidavit -- which may even require a notary -- makes it wholly impracticable, if not impossible to achieve."

New technology has made it easier to verify a person's voter registration status, and Hank is arguing that the state policy for rehabilitating a "stale and void" petition signature should reflect those changes.

Michigan now maintains a "qualified voter file," a computerized database that provides election officials with access to a interactive registration database.

Ballot committees should be able to prove registration status by submitting a qualified voter file report and a single affidavit signed by the preparer, according to Hank, who is requesting a review of the state policy.

The Board of Canvassers is scheduled to discuss his request at the state Capitol on Monday, according to a meeting agenda.

The board has the power to alter the policy it adopted in 1986, according to Woodhams, but its not clear whether members will want to do so.

Without a policy change, Hank said he will consider a legal challenge to the 180-day law itself, and he suggested that other Michigan groups that narrowly missed the ballot in past election cycles could be interested joining a suit.

"It's a wild political battle," Hank said.

Jonathan Oosting is a Capitol reporter for MLive Media Group. Email him, find him on Facebook or follow him on Twitter.