Colorado Attorney General Phil Weiser has joined a multistate coalition suing President Donald Trump over a new executive order on elections, arguing the directive unlawfully intrudes on states’ authority to run their own voting systems and threatens access to mail ballots for millions of voters.

The lawsuit argues that Trump’s executive order is unconstitutional because it intrudes on states’ authority to run their own elections and limits who can vote by requiring eligibility to be tied to a federally approved list.

“The president’s unlawful executive order threatens the right to vote for millions of Colorado voters—Democrat, Republican, or Unaffiliated—who use mail ballots,” said Weiser in a statement announcing the lawsuit. “The president does not have the power to takeover elections by signing an executive order. The Constitution is clear that the states determine the time, place, and manner of elections.”

The Colorado Attorney General’s Office has filed more than 50 lawsuits against the Trump administration.

On Tuesday, Trump signed an executive order establishing a national voter‑eligibility list and imposing new restrictions on mail voting. He has repeatedly criticized mail‑in voting systems, such as the one used in Colorado.

“The cheating on mail-in voting is legendary. It’s horrible what’s going on,” Trump said at a news conference, repeating allegations about the security of mail ballots as he signed the order.

Under Trump’s order, the U.S. Postal Service would be barred from sending absentee ballots to anyone not on the eligibility list.

The order also requires ballots to be placed in secure envelopes with unique barcodes for tracking.

Commerce Secretary Howard Lutnick joined Trump during Tuesday’s news conference to announce the latest executive order. Lutnick said states using mail-in voting systems must use the United States Postal Service.

“The states run these elections – if they want to use the U.S. mail, the U.S. Postal Service, they’re going to get a code, a bar code, from the US Postal Service and they’re going to put that on the envelope and we will have one envelope per vote,” Lutnik said.

The lawsuit challenging Trump’s order was filed in California. Joining the legal challenge are Massachusetts, Nevada, Washington, Arizona, Connecticut, Delaware, the District of Columbia, Illinois, Maine, Maryland, Michigan, Minnesota, New Jersey, New Mexico, New York, North Carolina, Oregon, Rhode Island, Vermont, Virginia, Wisconsin, and Pennsylvania.