A coalition of attorneys general from 14 states and the District of Columbia asked a federal judge to block the appointment of Acting Attorney General Matt Whitaker on Monday, the latest challenge to President Donald Trump’s efforts to replace former Attorney General Jeff Sessions.

In an amicus brief filed in U.S. District Court, the attorneys general voiced their support for the state of Maryland, which asked a federal judge to block Whitaker’s appointment earlier this month, saying it was illegal. Maryland, which is suing the federal government to uphold parts of the Affordable Care Act, has argued that the role should be filled instead by Deputy Attorney General Rod Rosenstein, who has already gone through the Senate’s confirmation process.

Whitaker has not been subject to the same vetting process, although the Justice Department has argued that it does not matter, as he is only serving in a temporary capacity under the Vacancies Reform Act.

The brief was signed by the attorneys general from Connecticut, Delaware, Hawaii, Illinois, Maine, Massachusetts, New Mexico, New York, North Carolina, Oregon, Pennsylvania, Rhode Island, Virginia, Washington state and the District of Columbia.

“Unfortunately, the legal controversy surrounding Mr. Whitaker’s appointment has threatened the legitimacy of the Department’s actions and the vital relationships between the Department and the States,” the brief, filed Monday, reads. “The Amici States therefore have an urgent interest in the resolution of this issue, so that no doubts surround the legitimacy and authority of the United States Attorney General and the United States Department of Justice.”

It continues: “The Amici States have concluded that Mr. Whitaker’s appointment is unlawful.”

Maryland has asked the U.S. District Court for the District of Maryland to issue an injunction that prohibits Whitaker from acting as attorney general.

“Who the attorney general is is at the core of this lawsuit,” the state’s attorney general, Brian Frosh (D), told The Washington Post earlier this month. “Aside from the constitutional issue, this guy, Mr. Whitaker, has extreme views and that’s dangerous in itself,”

Whitaker was appointed earlier this month after Sessions was forced to resign. Trump had spent more than a year berating his top law enforcement official over his decision to recuse himself from special counsel Robert Mueller’s probe of the 2016 election.

That investigation is now overseen by Whitaker, who has reportedly ingratiated himself with the president and publicly written about limiting the Mueller probe.

Whitaker has also come under fire for receiving more than $1.2 million from a shadowy conservative political group in the past few years, and some have questioned if he may have conflicts of interest that have not been aired in public.

Three senators have also filed their own lawsuit challenging the legality of Whitaker’s appointment ― Democratic Sens. Richard Blumenthal (Conn.), Mazie K. Hirono (Hawaii) and Sheldon Whitehouse (R.I.).

Read the full amicus brief below.