LANSING, MI -- Those petitioning voters for a spot on Michigan's ballot will have a strict 180 days to gather signatures under a law signed by Gov. Rick Snyder Tuesday.

SB 776, sponsored by Sen. Dave Robertson, R-Grand Blanc, codifies a 180-day deadline for collecting petition signatures. That's been standard practice, but this election cycle marijuana advocates dug up a catch: a laborious procedure established in the 1980's by which a group can prove its signatures older than 180 days are still valid and tied to registered voters.

MI Legalize asked the Board of State Canvassers to make the procedure easier to use so they would be able to rebutt signatures using a modernized, digital voter file instead of the 1980's system of gathering affidavits.

The Board of State Canvassers never acted, but the legislature went in the opposite direction and put the 180-day collection period into law with no exceptions. It was that law that Snyder signed Tuesday.

"Establishing reasonable time limits on when signatures can be collected helps ensure the issues that make the ballot are the ones that matter most to Michiganders," Snyder said in a press release.

MI Legalize turned in 146,413 signatures collected within the 180-day window and 137,029 older signatures they planned to rebutt. Theoretically adding those two numbers together could get the group over the 252,523 signatures it needs to get on the ballot.

But a report from the Secretary of State's staff to the Board of State Canvassers recommends the board certify the signatures as being insufficient, meaning it wouldn't get on the ballot. The board meets Thursday to vote on the matter.

The bill takes immediate effect. MI Legalize has hinted at legal action over the 180-day window.

Emily Lawler is a Capitol reporter on MLive's statewide Impact Team. You can reach her at elawler@mlive.com, subscribe to her on Facebook or follow her on Twitter: @emilyjanelawler.