The American Civil Liberties Union filed a federal lawsuit Wednesday on behalf of two New Hampshire college students seeking to block a controversial new requirement for voters in the state, saying it imposes an unconstitutional “poll tax” on voters and makes it disproportionately harder for students to cast a ballot.

In order to vote in New Hampshire, one needs to be “domiciled” there ― meaning they have a continued physical presence in the state that they intend to maintain. Being “domiciled” is legally different from being a “resident.” The state legally defines a resident as someone who intends to remain in the state “for the indefinite future.”

The new measure, HB 1264, which is set to take effect on July 1, removes the phrase “for the indefinite future” from the definition of resident and makes it identical to the definition of domiciled. Thus, anyone claiming to be “domiciled” in order to be eligible to vote is also saying they are a resident and is then obligated to required to get a driver’s license and register their car within 60 days.

The ACLU says the change is unconstitutional because it imposes a needless and unnecessary burden on college students and others who don’t plan to stay in the state permanently but want to vote there. The civil liberties group says the measure violates the First and 14th amendments because the state hasn’t “narrowly tailored” the law to advance a “compelling state interest.”

They also say it violates the 24th Amendment, which prohibits poll taxes, as well as the 26th Amendment, which grants the right to vote to anyone 18 or older.

Julie Ebenstein, a senior staff attorney at the ACLU Voting Rights Project, noted New Hampshire lawmakers had been trying for decades to impose similar restrictions on college students’ ability to vote. In 1972, a three-judge panel said a law that barred people who planned to leave a New Hampshire town at some point in the future from voting was unconstitutional. In 2014, a state court struck down a law that explicitly required anyone who registered to vote in New Hampshire to get a state driver’s license and to get their vehicle registered there. That decision was upheld by the New Hampshire Supreme Court.

New Hampshire Republicans passed HB 1264 shortly after Democrat Maggie Hassan defeated Republican Kelly Ayotte by 1,017 votes for one of the state’s U.S. Senate seats in 2016. In the same year, Democratic presidential candidate Hillary Clinton narrowly defeated Republican Donald Trump in the state. Ebenstein noted the bill passed along party lines in the legislature and that lawmakers appeared to be targeting young voters and college students based on a perception that they supported Democrats.

“College students are perceived by legislators as being more liberal or being more left and we know that because the legislators said so. ... Given legislators’ perception that young people are going to vote and are going to continue to vote a certain way, I think that’s why they’re being targeted,” she said in an interview. “The 2016 election was very close in New Hampshire.” She added that because of the state’s small population the 13,000 undergraduate students at the University of New Hampshire can make a difference in a close election.