CONCORD, N.H. (AP) — A lawsuit filed Monday challenges a New Hampshire law that would require proof of U.S. citizenship when registering to vote and photo identification when casting a ballot, saying it is one of the most restrictive voting laws in the nation.

The new law was set to take effect after the November elections. Republican Gov. Chris Sununu signed the bill earlier this month.

The lawsuit was filed by the American Civil Liberties Union of New Hampshire in U.S. District Court in Concord on behalf of the Coalition for Open Democracy, the League of Women Voters of New Hampshire, the Forward Foundation, and five voters. It names New Hampshire Attorney General John Formella and Secretary of State David Scanlan as defendants.

Laws like this that “create unconstitutional roadblocks to voting and which could stop thousands of eligible voters from participating in an election, have no place in our state,” Henry Klementowicz, deputy legal director at the ACLU of New Hampshire, said in a statement.

The lawsuit asks a judge to block enforcement, saying federal courts have weighed in on the matter before. A similar law in Kansas, which required proof of citizenship for state and federal elections, was found in 2018 to violate both the U.S. Constitution and the National Voter Registration Act.

However, in August 2024, the U.S. Supreme Court allowed some parts of a law requiring proof of citizenship to be enforced in Arizona as the legal fight continues in lower courts.

Under New Hampshire’s current law, those who don’t bring photo IDs to the polls can sign an affidavit attesting to their identity and are required to provide documentation within seven days. The new law would eliminate voter identification exceptions and would require those registering to vote to show a passport, birth certificate or other evidence of citizenship.

“This newly enacted voter registration requirement creates confusion, raises doubts for voters, and leaves them feeling hampered by the process,” Liz Tentarelli, president of the League of Women Voters New Hampshire, said in a statement Monday. “Instead of creating unnecessary barriers to voters, we need our elected officials to advance meaningful legislation that ensures New Hampshire voters can make their voices heard.”

A spokesperson for the state attorney general’s office, Michael Garrity said in a statement, “We will review the complaint and respond as appropriate.”

Sununu signed the bill on Sept. 12. It is set to become law two months after that.

“We have a proud tradition and proven track record of condition elections that are trusted and true,” he said at the time. “Looking forward to the next decade or two, this legislation will instill even more integrity and trust in the voting process.”

Voting by noncitizens is prohibited in federal elections and is not allowed in any state elections, although a handful of municipalities nationwide allow it in limited circumstances. While illegal voting by noncitizens is extremely rare, the possibility that it could happen on a wider scale because of the influx of migrants at the southern border has become a theme of Republican campaign messaging this year.

In Washington, Republicans are trying to push through the SAVE Act, a proof-of-citizenship mandate for voters, as part of wider legislation aimed at avoiding a partial government shutdown this fall.