Hawaii Attorney General Russell A. Suzuki has joined a coalition of 15 attorneys general challenging President Donald Trump’s appointment of Matthew Whitaker as acting attorney general of the United States.

The coalition filed an amicus brief today in U.S. District Court in Maryland, arguing that Whitaker’s appointment violates laws clearly indicating that the chief deputy attorney general takes over when an attorney general steps down or is removed.

“Mr. Whitaker’s appointment as Acting Attorney General of the United States is unlawful and threatens the legitimacy of activities undertaken by the Department of Justice.” said Suzuki in an e-mailed statement.

The amicus brief supports Maryland’s motion for a preliminary injunction in a lawsuit regarding the Affordable Care Act that could impact Americans with preexisting conditions. The motion seeks to stop Whitaker from exercising the authority of the U.S. attorney general and to substitute Deputy Attorney General Rod Rosenstein as a defendant in the lawsuit between Maryland and the federal government.

It states that Whitaker’s appointment is illegal, ignores long-established vacancy succession laws, and is in violation of Congress’ clear designation of the deputy attorney general as the acting attorney general.

“The relationship between the Justice Department and the States is so essential—whether it is collaborative or adversarial—that any doubts about the legitimacy of the Acting Attorney General threaten to harm the Amici States,” said the brief. “That is why the identity of the legitimate Acting Attorney General must be resolved as soon as possible. To allow doubts about the legality of Mr. Whitaker’s appointment to linger is to invite legal challenges to both significant and routine actions undertaken by the Department while he is serving as Acting Attorney General.”

The attorneys general also noted that Congress has protected the Senate’s confirmation power by specifying that in the event of a vacancy in the U.S. Attorney General’s office, the Senate-confirmed deputy attorney general, if available, temporarily assumes the position until a new appointee is confirmed. This specific order of succession in the U.S. Attorney General’s office, the brief said, has been established since the Department of Justice was first established in 1870 to maintain continuity of government.

Suzuki joined the attorneys general of the District of Columbia, Pennsylvania, New York, Connecticut, Delaware, Illinois, Maine, Massachusetts, New Mexico, North Carolina, Oregon, Rhode Island, Virginia, and Washington in the suit.