MONTANA — A Montana judge blocked the state from enforcing a new law that would have limited voter registration on Election Day. District Judge Adam Larsen issued the order late Friday, keeping registrations open through the trial of a lawsuit filed by the Montana Federation of Public Employees, which was later joined by the Blackfeet and Northern Cheyenne tribes.

The Republican-controlled Legislature enacted the law last year. It would have prevented voters from casting ballots in presidential, U.S. Senate and U.S. House races if they registered after noon on Election Day. The state's primary elections are scheduled for June 2, and the trial is scheduled for late August.

"Registering on Election Day is wildly popular," Larsen wrote. "The undisputed record demonstrates that a substantial number of Montana voters rely on Election Day registration, including during afternoon hours."

He pointed to obstacles that some voters would face under the noon cutoff. Larsen wrote that Native American voters face unique barriers to voting, including long travel distances and limited access to transportation, and that students and other young voters face obstacles to registering because of scheduling constraints and because they move more frequently. Larsen rejected the state's argument that the law would make administering elections easier.

Montana polling places serving at least 400 voters must remain open from 7 a.m. to 8 p.m. on Election Day, while polling places serving fewer voters may open at noon.

The plaintiffs also challenged changes in a state law specifying which IDs students can show at the polls to register and vote. Larsen concluded that they could not show that anyone had been prevented from voting because of those ID changes.

Montana Attorney General Austin Knudsen's office expressed disappointment in the ruling. "Unrestricted voter registration on Election Day puts a undue burden on Montana's election administrators who have very important jobs ensuring our elections are secure and run smoothly," spokesperson Chase Scheuer said in an email. Scheuer said the changes "bolster the integrity of Montana elections."

It was the second time in five years that legislators attempted to move away from Election Day registrations. Montana has allowed Election Day voter registration since 2006. In 2014, 57% of Montana voters rejected a statewide ballot initiative to end the practice. In 2021, the Legislature enacted a law ending voter registration at noon the day before Election Day. The Montana Supreme Court struck down that 2021 law in 2024 as a violation of an "unequivocal fundamental right" protected by the state Constitution. The justices noted that more than 70,000 Montana voters had used Election Day registration since its inception. Before enacting the latest law in 2025, legislative staff warned in a memo that the measure could conflict with the Supreme Court's 2024 decision.