Senate Democrats on Monday sued President Trump to block his decision to name Matt Whitaker as acting attorney general.

Sens. Richard Blumenthal, D-Conn., Sheldon Whitehouse, D-R.I., Mazie Hirono, D-Hawaii, filed the lawsuit in the U.S. District Court for the District of Columbia on Monday. In the 17-page complaint, Democrats said Whitaker’s appointment by President Trump earlier this month violates the Appointments Clause of the U.S. Constitution.

The clause requires that the Senate confirm high-level federal government officials, including the attorney general, before they exercise the duties of the office.

“The U.S. Senate has not consented to Mr. Whitaker serving in any office within the federal government, let alone the highest office of the DOJ,” the Democrats said in their complaint.

The lawmakers are represented by two non-partisan and non-profit law firms in the case: Protect Democracy and the Constitutional Accountability Center.

“Indeed, before deciding whether to give their consent to Mr. Whitaker serving in such a role, Plaintiffs and other members of the Senate would have the opportunity to consider his espoused legal views, his affiliation with a company that is under criminal investigation for defrauding consumers, and his public comments criticizing and proposing to curtail ongoing DOJ investigations that implicate the President,” the complaint said.

Rather than appoint Deputy Attorney General Rod Rosenstein to replace former Attorney General Jeff Sessions, Trump invoked a provision in the Federal Vacancies Reform Act to appoint Whitaker.

Last week, a memo from the Justice Department’s Office of Legal Counsel upheld Whitaker’s temporary role leading the department. But Democrats said this goes against the Constitution.

“Installing Matthew Whitaker so flagrantly defies constitutional law that any viewer of School House Rock would recognize it. Americans prize a system of checks and balances, which President Trump’s dictatorial appointment betrays,” Blumenthal said in a Monday statement. “President Trump is denying Senators our constitutional obligation and opportunity to do our job: scrutinizing the nomination of our nation’s top law enforcement official. The reason is simple: Whitaker would never pass the advice and consent test. In selecting a so-called “constitutional nobody” and thwarting every Senator’s constitutional duty, Trump leaves us no choice but to seek recourse through the courts.”

Last week, top congressional Democrats slammed the OLC opinion, and said Rosenstein should have been automatically named.

Sen. Dianne Feinstein, the top Democrat on the Senate Judiciary Committee, also demanded a hearing with both Whitaker and Sessions.

In addition to Democratic Senators hitting Whitaker and the Trump administration, Democrats on the House Judiciary and Oversight Committees have also made it clear that there are questions to be answered.