The Justice Department released a legal opinion last week that said Whitaker's appointment would not violate the clause because he is serving in an acting capacity. The opinion concluded that Whitaker, even without Senate confirmation, may serve in an acting capacity because he has been at the department for more than a year at a "sufficiently senior pay level."
"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," Blumenthal said in a statement. "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."
The lawsuit comes days after a Washington lawyer challenged Whitaker's appointment in a pending Supreme Court case dealing with gun rights. The attorney, Thomas Goldstein, asked the high court to find that Whitaker's appointment is unconstitutional and replace him with Deputy Attorney General Rod Rosenstein.
The state of Maryland also made a similar court filing last week in a legal dispute with the Trump administration over the Affordable Care Act.
Rosenstein, the second-ranking Justice Department official, has been confirmed by the Senate and had been overseeing special counsel Robert Mueller's Russia investigation. Whitaker is now overseeing the investigation.