An absentee ballot requirement that has resulted in thousands of Montana votes being thrown out since 2025 was ruled unconstitutional Monday by a state judge.

At issue is the requirement that voters write their birth year on absentee ballot return envelopes. In his Monday ruling, Lewis and Clark County District Court Judge Mike Menahan said the requirement had disenfranchised nearly 6,000 Montana voters since it was created by the 2025 Legislature.

The ruling means that 2026 general election ballot envelopes missing the birth year won’t be rejected. The first day voters could walk into a polling place and receive an absentee ballot was Monday. Elections administrators will mail absentee ballots to voters on the absentee list on Friday, Oct. 9.

In making the birth year requirement law, legislators argued that the information would prevent voter fraud. Rep. Braxton Mitchell, R-Columbia Falls, proposed the requirement. Menahan ruled that the state failed to prove the requirement prevented fraud, even as voters’ ballots were being rejected for omitting their birth years.

The lawsuit was brought by Disability Rights Montana and Big Sky 55+, groups that represent people with disabilities and seniors. Montana Secretary of State Christie Jacobsen, the state’s top election official, defended the law on the state’s behalf in court.

“The state does not explain how or why the addition of a birth year promotes public confidence and does not offer any evidence in support of its position,” Menahan said in the order. “In response, Disability Rights argues the birth year requirement damages public confidence in elections because it has resulted in thousands of ballots being discarded due to missing or incorrect birth years.”

Quoting the U.S. Supreme Court, Menahan wrote that the “discarding of lawful (votes) erodes public confidence that the election results reflect the people’s will.”

Election administrators said the birth year requirement first disqualified ballots during municipal elections in fall 2025. At the time, Sarah Bell, Missoula County’s deputy elections administrator, told Montana Free Press that the requirement produced a tenfold increase in rejected ballots compared with the primary, which was held before the new rule took effect.

Some county election offices assigned employees to call, email or write voters whose mailed absentee ballots were missing birth years.

In some communities, the number of rejected ballots was large enough to potentially change election outcomes. In Billings, for example, the 2025 mayoral race was decided by 200 votes, while 627 ballots were not counted because they lacked birth years.

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This story was originally published by Montana Free Press and distributed through a partnership with The Associated Press.