Ten Republican senators in Oregon cannot run for reelection, the state’s top court ruled on Feb. 1.

The court found that the senators are banned from running for reelection under a constitutional amendment approved in 2022.

The amendment, Ballot Measure 113, states that lawmakers who miss at least 10 legislative days without an excuse cannot seek reelection.

The ruling upheld a decision from Oregon Secretary of State LaVonne Griffin-Valade, a Democrat.

Ms. Griffin-Valade said in 2023 that the senators, under the measure, could not try for another term after their current term.

“My decision honors the voters’ intent by enforcing the measure the way it was commonly understood when Oregonians added it to our state constitution,” she said at the time.

The decision sparked a lawsuit from some of the Republican senators, but the Oregon Supreme Court sided with the secretary of state.

“Because the text is capable of supporting the secretary’s interpretation, and considering the clear import of the ballot title and explanatory statement in this case, we agree with the secretary that voters would have understood the amendment to mean that a legislator with 10 or more unexcused absences during a legislative session would be disqualified from holding legislative office during the immediate next term, rather than the term after that,” the new ruling reads.

Justices said they used their typical methodology in construing the amendment “by determining how the voters who adopted the amendment most likely understood its text.” The method included considering the information presented to voters, which stated that voting yes would disqualify legislators with 10 unexcused absences for the term “following current term in office.”

“Those other materials expressly and uniformly informed voters that the amendment would apply to a legislator’s immediate next terms of office, indicating that the voters so understood and intended that meaning,” the justices wrote.

The ruling applies to 10 Republican senators in the 30-seat body.

“I’ve said from the beginning my intention was to support the will of the voters,” Ms. Griffin-Valade said in a statement. “It was clear to me that voters intended for legislators with a certain number of absences in a legislative session to be immediately disqualified from seeking reelection. I’m thankful to the Oregon Supreme Court for providing clarity on how to implement Measure 113.”

Oregon Senate President Rob Wagner, a Democrat, said that the ruling “means that legislators and the public now know how Measure 113 will be applied, and that is good for our state.”

The senators in question, including state Senate Minority Leader Tim Knopp, missed more than 10 days in 2023 while protesting Democrat-sponsored bills on abortion and other issues. Their walkout of about six weeks delayed voting because it resulted in a lack of quorum, or the minimum number of senators needed to be present to hold a vote.

“We obviously disagree with the Supreme Court’s ruling. But more importantly, we are deeply disturbed by the chilling impact this decision will have to crush dissent,” Mr. Knopp said on Feb. 1.

Oregon voters approved Measure 113 by a wide margin following Republican walkouts in the Legislature in 2019, 2020, and 2021.

The measure says disqualification applies to “the term following the election after the member’s current term is completed.”

Mr. Knopp and others had challenged the interpretation of the measure.

Lawyers for the senators said they viewed the measure language as meaning that the lawmakers could run in 2024, since a senator’s term ends in January while elections are held the previous November. They argued the penalty doesn’t take effect immediately, but rather, after they’ve served another term.

All parties in the suit had sought clarity on the issue before the March 2024 filing deadline for candidates who want to run in this year’s election.

Mr. Knopp and three other Republican senators had already launched reelection bids before the case was considered, while two other senators have said that they’re retiring at the end of their terms. The remaining GOP senators were elected in 2022 for terms that end in early 2027, so they will be barred from running in 2026.

Justice Aruna Masih didn’t participate in the consideration of the case or the decision, the Oregon Supreme Court stated.

All justices on the Oregon Supreme Court were appointed by Democrat governors, either Gov. Kate Brown or Gov. Tina Kotek.

“I’m disappointed but can’t say I’m surprised that a court of judges appointed solely by Gov. Brown and Gov. Kotek would rule in favor of political rhetoric rather than their own precedent,” said state Sen. Suzanne Weber, another lawmaker affected by the ruling. “The only winners in this case are Democrat politicians and their union backers.”

Another challenge from Republicans, this one in federal court, is still pending. The court recently denied a preliminary request that would have let three of the Republicans run, a decision the Republicans have appealed.