WASHINGTON — The Justice Department pushed back on Wednesday against accusations that President Trump’s appointment of Matthew G. Whitaker as acting attorney general was illegal, arguing that it complied with both federal statutes and the Constitution — and that it fit within a history of similar designations dating back to the earliest days of the country.
The Trump administration made its case in a 20-page memorandum by Steven E. Engel, the head of the department’s Office of Legal Counsel. It came a day after the State of Maryland asked a Federal District Court judge to issue an injunction declaring that when Mr. Trump ousted former Attorney General Jeff Sessions, the role of acting head of the department passed instead to the deputy attorney general, Rod J. Rosenstein, as a matter of law.
But even as the Trump administration offered its most fulsome argument to date that Mr. Whitaker’s designation as acting head of the Justice Department was lawful, it continued to sidestep questions about whether ethics rules required Mr. Whitaker to recuse himself from overseeing the special counsel investigation by Robert S. Mueller III into whether Mr. Trump’s associates conspired with Russia in its election interference.
Mr. Whitaker has been an outspoken critic of the investigation, making clear that he has already decided that no Trump associates conspired with Moscow’s election disruption. He unsuccessfully interviewed in 2017 for the job of the White House’s top lawyer defending against the inquiry, and is friends with Sam Clovis, a witness in the investigation.
Top congressional Democrats sent a letter to the Justice Department’s ethics chief, Lee J. Lofthus, demanding any analysis or advice he gave Mr. Whitaker about whether to recuse, but they have received no response.
On Wednesday, several senators were expected to try to bring up a long-stalled bill that would allow special counsels like Mr. Mueller, if fired, to appeal their dismissal to a panel of judges and possibly be reinstated. Its chances of passage were seen as dim. Also on Wednesday, several leading House Democrats announced an investigation into Mr. Whitaker’s involvement with World Patent Marketing, a defunct company accused of defrauding customers of millions of dollars before a judge shut it down last year.
Mr. Engel’s memo, released on Wednesday, addressed only the legal issues related to Mr. Whitaker’s appointment. It laid out a vision for sweeping presidential power to temporarily replace any Senate-confirmed official and install in his or her place a person outside the normal order of succession and who has not undergone Senate vetting.
The memo was dated Wednesday but Mr. Engel wrote that his office had verbally advised the White House that the president had lawful authority to designate someone like Mr. Whitaker as the acting successor to Mr. Sessions before he resigned under pressure last week. The memo did not say when the White House first asked for such analysis, and the Justice Department declined to provide additional details.
Mr. Trump’s selection of Mr. Whitaker to be the nation’s top law enforcement official has drawn two types of legal criticism from commentators and in the Maryland court filing.
The state rejected Mr. Engel’s analysis, said Rachel Coombs, a spokeswoman for Maryland’s attorney general, Brian E. Frosh. “Of course we disagree with the memo and the reasons we disagree are outlined in our motion filed yesterday,” she wrote in an email on Wednesday.
Critics have made a legal argument against Mr. Whitaker’s appointment. Congress has enacted a law that addresses the order of succession for attorney general. It says that the deputy attorney general — Mr. Rosenstein — takes over as acting head of the department in the case of a vacancy. But Mr. Trump installed Mr. Whitaker under a provision of the Vacancies Reform Act of 1998, a separate law that applies to the executive branch in general.
Critics of the appointment have argued that the more specific law that addresses the Justice Department makes the position of attorney general an exception to the procedures listed in the more general Vacancies Reform Act. But Mr. Engel argued that the better interpretation was that the president can pick either option.
In support of that argument, he cited litigation over disputes involving the position of acting general counsel for the National Labor Relations Board and the acting head of the Consumer Financial Protection Board. In those cases, lower-court judges ruled that the Vacancies Reform Act mechanisms for temporarily filling vacancies remained available as an alternative to other statutes that specifically addressed those offices.
“For these reasons, we believe that the president could invoke the Vacancies Reform Act in order to designate Mr. Whitaker as acting attorney general ahead of the alternative line of succession provided” in the attorney general succession statute, Mr. Engel wrote.
Another legal argument is constitutional. Some legal commentators have argued that under the Constitution’s appointments clause, only an official whom the Senate confirmed for his or her current position can be temporarily elevated to acting attorney general. Mr. Whitaker did not require confirmation for his previous role as Mr. Sessions’s chief of staff.
But Mr. Engel argued that Supreme Court precedent and historical practice showed that when the position of a principal officer — one who is very senior and powerful, and which normally requires confirmation, like attorney general — is vacant, someone who has not been Senate-confirmed may temporarily fill it.
In support of that claim, Mr. Engel pointed to an 1898 Supreme Court case upholding the temporary appointment of a replacement consul in modern-day Thailand who had not been confirmed by the Senate after the consul in place grew dangerously ill and had to leave the country.
He pointed to statutes dating back to George Washington’s administration in which Congress authorized presidents to direct certain officials without Senate confirmation to temporarily carry out the duties of vacant principal officers. And, he said, Justice Department research had identified more than 160 occasions before the Civil War in which presidents had designated non-Senate-confirmed officers to serve as acting principal officers, along with many more in more recent years.
Mr. Engel’s memo identified no examples of an acting attorney general who had not undergone Senate confirmation since Congress created the Justice Department in 1870. But he cited a six-day period in 1866 when an assistant without Senate confirmation temporarily replaced Attorney General James Speed, who had resigned.
“It is no doubt true that presidents often choose acting principal officers from among Senate-confirmed officers,” Mr. Engel wrote. “But the Constitution does not mandate that choice.”