Washington CNN  — 

The Justice Department issued a defense of President Donald Trump’s controversial appointment of Matt Whitaker as acting attorney general Wednesday, offering several reasons why the appointment is consistent with the Constitution, federal statutes and past precedent.

The memo provides a robust legal justification for Whitaker’s right to lead the Justice Department, which includes ultimate oversight authority over special counsel Robert Mueller.

In a 20-page memo addressed to the White House from DOJ’s Office of Legal Counsel – the chief legal interpreter of federal law for the administration – the department concludes that:

* Whitaker’s appointment is consistent with the plain terms of the Vacancies Reform Act, “because he had been serving in the Department of Justice at a sufficiently senior pay level for over a year” as the statute requires.

* Whitaker is only serving on a temporary basis, so he wasn’t required to be confirmed by the Senate ahead of his selection last week, though the Justice Department acknowledged that situation had not come up in over a century. DOJ found that in 1866, a non-Senate confirmed assistant attorney general served as acting attorney general, before the department was founded.

* Even though a separate statute exists that provides a succession plan at the Justice Department, the President can choose someone else consistent with the Vacancies Act.

A senior Justice Department official said Wednesday that prior to Jeff Sessions’ firing last week, the White House requested oral advice on whether the President could designate a senior DOJ official to serve as acting attorney general, but declined to provide details on when exactly that conversation occurred or whether Whitaker was specifically contemplated. The official would only confirm that this written memo is consistent with that oral advice.

The memo comes a day after the state of Maryland challenged Whitaker’s appointment, arguing that Trump wrongfully bypassed the Constitution by appointing Whitaker to replace Sessions and that Deputy Attorney General Rod Rosenstein is Sessions’ rightful successor.

It does not specifically address the questions that have been raised in recent days about whether Whitaker must recuse himself from overseeing Mueller given his past criticisms of the Russia investigation.