An op-ed co-written by George Conway — husband of White House counselor Kellyanne Conway — contends that President Trump’s appointment of Matthew Whitaker as acting attorney general is unconstitutional because he wasn’t confirmed by the Senate.

“It’s illegal. And it means that anything Mr. Whitaker does, or tries to do, in that position is invalid,” Conway, a lawyer, wrote with Neal K. Katyal, an acting solicitor general under President Barack Obama, in a column published Thursday by The New York Times.

Whitaker, who has been critical of special counsel Robert Mueller’s Russia investigation, now reports directly to the president, and therefore is what is known as a “principal officer” under the Constitution’s “Appointments Clause,” the pair argued.

“We cannot tolerate such an evasion of the Constitution’s very explicit, textually precise design. Senate confirmation exists for a simple, and good, reason. Constitutionally, Matthew Whitaker is a nobody. His job as Mr. Sessions’s chief of staff did not require Senate confirmation,” they wrote.

“For the president to install Mr. Whitaker as our chief law enforcement officer is to betray the entire structure of our charter document.”

Conway, a Trump administration critic, recently claimed the president can’t unilaterally end “birthright citizenship.”