I forgot to add the Iowa Rules of Professional Conduct provision which states: (d) Except as law may otherwise expressly permit, a lawyer currently serving as a public officer or employee:

(1) is subject to rules 32:1.7 and 32:1.9; and

(2) shall not:

(i) participate in a matter in which the lawyer participated personally and substantially while in private practice or nongovernmental employment, unless the appropriate government agency gives its informed consent, confirmed in writing;

I've dealt with this issue before (succession questions), so the wording here has both legislative and legal significance which is different than posited.

The "may" is permission from the legistature to conduct the business on behalf of the agency/United States, not to give the Deputy, or anyone else, discretion to do so or not. This is to prevent the agency from being unable to conduct business because the head of the agency is absent. In some agencies, duties of the "principal" may not be delegated (there are several for the A.G. that are exclusive to him/her). This changes that so that, for example, the Deputy A.G. is allowed to supervise the Special Counsel because the A.G. is unable to, since that supervision is exclusive to the A.G.

The problem with Whitaker, which Maryland has raised, is that if he is not a legal choice for the position he cannot conduct business as head of the agency (e.g. may not). In that case only the Deputy A.G. can conduct that business.

Although there is a corner-case basis for appointing Whitaker, there are at least three that preclude him from doing so. I say that, although the DOJ under Gonzales issued an opinion that argued otherwise (using, as was the Bush way, bad legal analysis). That issue was not, to my knowledge, litigated as his appointed "successor" only served for two months. It is the nature of the GOP to use legal legerdemain to pervert or avoid actually applying the law as written.

DOJ has provided a justification for appointing Whitaker: Memo. Shockingly, they justified it (remember that "corner-case" argument?)!

Trump has plenty of Justice Department lawyers who will justify Trump positions that then go on to lose in court. I wonder if they are doing their whole job and advising the White House that their justification will probably lose in court. Or worse, that everyone will laugh at it before it loses in court.

I've been mulling and researching this issue since it happened. I am still convinced that the appointment is both illegal and unconstitutional (as well as unethical). The justification by the DoJ, while wordy, is spurious. If there is interest, I'll provide a complete analysis, but the upshot is this: 1) the Constitution provides that "principal officers" (that report directly to the President) must have the "advice and consent" of the Senate- there are, literally,
100 members of the DoJ that meet this requirement (Whitaker is not one of them); 2) the DoJ succession statute lists the order of succession - which are all Senate-confirmed (Whitaker is NOT on that list). It also addresses one section of the Vacancies Act specifically by noting that the Deputy AG (Rosenstein) is the "first assistant" for purposes of the Act, but mentions no other provisions, a notable omission; 3) the Vacancies Act is a general statute, rather than a specific one (As the DoJ succession statute is), and specific laws take precedence over general laws; moreover, the Vacancy Act specifically acknowledges this and provides "that Section 3347 provides that the Vacancies Act is exclusive unless “a statutory provision expressly” authorizes “an officer or employee to perform the functions and duties of a specified office temporarily in an acting capacity.”; 4) all statutes are inferior to the Constitution.

Apparently Republicans use a different dictionary than you or I.

I have to applaud xAG Sessions, even though I strongly disagreed with almost everything he stood for, on having enough integrity to follow advice of DoJ ethics and recluse himself.

Too bad other Republicans can not or will not consider their positions as conflicts of interest and recluse themselves.

I doubt it was ethics: He saw some bad stuff and wanted to get enough distance so he will not go to prison for it. It was probably stuff he should have acted on, but now he's probably in the clear considering all the truly horrendous stuff that came after that. The man is a lawyer, after all. He is probably reasonably competent at judging the kind of stuff that gets lawyers disbarred or sent to jail.

Today's reporting causes this issue to rear its ugly head. Paul Manafort’s Lawyer Told Trump Team What His Client Said To Mueller: Report (HuffPo). The details of this are quite disturbing, because it may constitute an ethics violating of this lawyer, and it combines with Corsi releasing the proposed deal from Mueller probe (What new draft court docs reveal about Mueller's case - CNN). Roger Stone and Jerome Corsi are in deep. It now ALSO appears that Trump had been actively obstructing justice through Manafort, Stone, Corsi, their attorneys, and acting AG Whitaker. This criminal conspiracy is growing. The parallels to Watergate are becoming unavoidable.