Maine Attorney General Aaron Frey has joined a multistate lawsuit challenging President Donald Trump’s executive order to overhaul election rules nationwide.

The March 25 order includes requiring documentary proof of citizenship to register to vote in federal elections and demanding that all absentee ballots be received by Election Day.

Trump’s order says the U.S. has failed “to enforce basic and necessary election protections” and calls on states to work with federal agencies to share voter lists and prosecute election crimes. It threatens to pull federal funding from states where election officials don’t comply.

Frey joined a coalition of 19 attorneys general Friday in filing a lawsuit against Trump and other federal officials, arguing that the order is unconstitutional and infringes on the rights of individual states to administer elections.

“The president has no constitutional power to rewrite state election laws by decree, nor does the president have the authority to modify the rules Congress has created for elections,” the coalition said in a news release. The lawsuit was filed in the U.S. District Court in Massachusetts.

“The right to vote is a cornerstone of our free society and the president is acting without any authority by trying to dictate election law,” Frey said in a written statement. “If the president and his administration have their way, Mainers will have a harder time casting their ballot.”

Other states joining the suit include Arizona, California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Massachusetts, Maryland, Michigan, Minnesota, Nevada, New Jersey, New Mexico, New York, Rhode Island, Vermont and Wisconsin.

Maine Secretary of State Shenna Bellows also has criticized the executive order, saying it would make it harder for women, military members, overseas voters and rural citizens to vote.

In Maine, people must show proof of their identity and age, such as a driver’s license or passport, to register to vote. They also must show proof of residency, which can be documented a number of ways, including with a utility bill, bank statement, paycheck, driver’s license, motor vehicle registration, or hunting or fishing license.

But the order’s requirement to show proof of citizenship has raised concerns about disenfranchising voters, especially married women who have changed their names but whose birth certificates still list their maiden names.

“I have serious concerns about the policies proposed in the executive order that would make it harder to vote for women, military and overseas voters and rural citizens,” Bellows said.

Maine law already requires that absentee ballots be received by the time polls close on Election Day, but 18 states and Puerto Rico allow ballots postmarked on Election Day to be counted.

The new lawsuit comes as Frey has already joined several other legal challenges to Trump’s executive orders and disruptions to federal funding.

Frey and the other attorneys general won a ruling in a different case Thursday, when a federal judge temporarily blocked the Trump administration from cutting more than $11 billion in public health grants allocated to U.S. states during the COVID-19 pandemic.

Maine stands to lose $91 million federal funding as part of that nationwide cut. As a result, the Maine Center for Disease Control and Prevention is laying off at least 40 subcontracted workers and reducing capacity in a number of public health services, including vaccine distribution, infectious disease tracking and outbreak management.