From the abstract of Andrew McCanse Wright’s Justice Department Independence and White House Control (2018):
Problematic relations between the White House and the U.S. Department of Justice stand out amidst the broader tumult of President Donald Trump’s first year in office. With respect to written policy restricting contacts between the White House staff and the Department, the Trump White House has followed the general contours of predecessor administrations. Those policies recognize that White House contacts restrictions vary with the Department’s complex functions, restrict channels of contact, and restrict personnel authorized to make contacts. They also grant limited exceptions where White House-Department contact is required to assist the President in the performance of a constitutional duty and contact would be appropriate from a law enforcement perspective. A number of episodes, however, suggest that the President and senior administration officials have not honored the spirit, and in some cases the letter, of that contacts policy.
One of the frequent criticisms leveled against President Trump is that he disregards many norms and traditions that have been observed by presidential administrations of both parties for decades. Restrictions on White House interference in criminal investigations do not merely protect norms. Rather, those policies also seek to prevent unconstitutional conduct by the President and his political appointees. This Article demonstrates that political interference by the President undertaken in bad faith could violate the Take Care Clause even in the absence of a criminal statute. Obstructive behavior is even worse. Whether or not the President is indictable for the commission of a statutory criminal offense of obstruction of justice during his tenure in office, this Article explains why the President may violate the Take Care Clause independently of criminal offenses.
A principle of political noninterference by the White House in the federal prosecution function in particular matters is consistent with Article II. Neither the Vesting Clause, the President’s position atop the Executive Branch, nor the President’s broader enforcement discretion defeat the anti-interference principles commanded by the Presidential Oath and the Take Care Clause. It is a question that goes to the very concept of Rule of Law itself. However, political processes, rather than justiciable legal proceedings, serve as the presumptive source of Take Care Clause enforcement as to White House-Department relations.