BISMARCK, N.D. (AP) — People in their late 70s or older can no longer run for Congress in North Dakota under a ballot measure overwhelmingly approved by voters Tuesday, and legal scholars said the law could remain on the books indefinitely because no elderly candidate might challenge the restriction they deem likely unconstitutional.

Those experts view the constitutional amendment as an effort to revisit a nearly 30-year-old Supreme Court ruling against congressional term limits and could provide a potential test case for the nation. The initiative bars people from running or serving in the U.S. House or Senate if they are to turn 81 years old during their term.

The high-profile measure comes at a time when the ages of elderly officeholders have been front and center in the presidential race between Joe Biden and Donald Trump. Lawmakers including Sen. Dianne Feinstein, who died last year, and Senate Minority Leader Mitch McConnell also have drawn attention to the issue because of their ages and health issues.

For now, the age limit stays on the books until somebody challenges it, said David Schultz, professor of political science at Hamline University and a law professor at the University of Minnesota specializing in election and constitutional law. He said the key to any challenge would be who has standing to bring a claim.

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“This is like really the picky stuff of a law professor now, of the ‘who actually gets to get into the courthouse door?’” Schultz said.

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He said he views the measure as unconstitutional under the 1995 term limits decision that states cannot set qualifications for Congress beyond what is already in the U.S. Constitution.

He said a potential challenge could come from someone barred by the age limit in an election — or potentially a political party seeking to nominate an older candidate. But he added any group filing suit, such as an organization representing older people, would have to show how it is harmed by the age limit.

The measure is to take effect immediately although election results still must be certified. Independent candidates have until September to file signatures to appear in the 2024 general election, meaning an age-barred candidate could theoretically emerge and be denied. The North Dakota Supreme Court would have jurisdiction over an appeal under the measure.

Schultz sees federal court as the likely path for any lawsuit. A judge and Court of Appeals would both likely be bound by the 1995 term limits ruling, he said. Then it would be a question of whether the U.S. Supreme Court takes it, he said.

“I wouldn’t be surprised if a ton of money appears on both sides as it moves up the appellate chain because I’m suspecting there are interests on both sides here that would like to see the law upheld and like to see the law struck down,” Schultz said.

A state legislative panel, anticipating a lawsuit, estimated it would cost the state $1 million to defend the age limit.

The measure is vexing in two ways, said Michael Thorning, director of the Structural Democracy Project at the Bipartisan Policy Center. It seems clear that even the initiative’s proponents know it’s likely in contradiction to the 1995 ruling. But Thorning said it’s also perplexing why supporters of the measure didn’t apply the age limit to state or local officers or presidential candidates “if they are concerned or confident about their argument.”

It’s unclear what groups outside North Dakota or “existing constituency” would look to challenge the age limit, Thorning said. Various points could be raised, such as elderly congressmembers who are among the most effective, and whether the state constitution would now violate the equal protection clause of the 14th Amendment, Thorning said.

Notably, conservative Justice Clarence Thomas is the only member of the Supreme Court remaining from the 5-4 term limits ruling in 1995, in which he dissented, he said.

Jared Hendrix, who chaired the sponsoring committees of the age limit measure and a successful gubernatorial and legislative term limits initiative in 2022, said he thinks there probably will be a challenge, but that would depend on somebody with standing. Hendrix said the group chose 80 as the maximum age because support at that point is overwhelming.

A federal lawsuit could theoretically take years, but the courts have sometimes shown an unusual amount of speed when it comes to ballot access or candidate qualifications, such as former president Trump’s eligibility in some states under the U.S. Constitution’s insurrection clause, Thorning said.

U.S. Sen. Kevin Cramer, R-N.D., who is seeking reelection, opposed the measure. He said the age limit would arbitrarily limit voters’ choices.

“In fact, to me, things like term limits are promoted by lazy democracy. The greatest part of our system is our self-governance, which is embodied in voting and electing people and making your own decisions,” said Cramer, 63.