From the abstract for Mark Greenberg, Can Trump Obstruct Justice?, NYR Daily, Jan. 4, 2018:
Can a president commit obstruction of justice by terminating a criminal investigation? This question has become critical to the future of the Trump presidency.
When considering whether it is possible for the president to commit obstruction of justice by terminating an investigation, legal experts feel the pull of two conflicting ideas. On the one hand, it seems clear that a president who orders subordinates to lie to the FBI, destroys evidence, or bribes witnesses has committed obstruction of justice. This idea leads to the straightforward view that if the president acts with the corrupt purpose required for obstruction of justice, he can be guilty of that crime just as anyone else can. This republican view of presidential powers is probably the one held by most experts.
On the other hand, one may think that surely the president must be special by virtue of the Constitution’s broad grant of executive power. The executive branch would be unduly hampered if there were constant scrutiny of the president’s motives in exercising his authority. But an embrace of this idea without qualification leads to a royalist view of presidential powers.
Several others — including two former Justice Department officials, David B. Rivkin Jr. and Lee A. Casey, writing in The Wall Street Journal, but most notably Harvard Law professor emeritus Alan Dershowitz — have advocated a more nuanced position that seems to reconcile the two conflicting ideas, what I call the protected act view. Dershowitz rejects the royalist position: a president who lies to the FBI or authorizes the bribery of a witness is not exercising a power granted to the president by the Constitution, and therefore can be guilty of obstruction of justice. At the same time, Dershowitz argues that presidential actions “within [the president’s] constitutional authority,” such as firing an executive official or terminating an investigation, cannot be an obstruction of justice; in fact, a president acting within that authority, regardless of his purposes, cannot violate the law.
The protected act view has important implications for a potential impeachment proceeding. The constitutional standard for an impeachable offense — “treason, bribery, or other high crimes and misdemeanors” — is best understood to require serious official misconduct, but not the commission of a crime. But since Dershowitz’s protected act view implies that any presidential termination of an investigation is constitutionally authorized, impeachment for such an action could not be legally permissible. The view thus implies a constitutional bar to impeachment as well as to criminal prosecution.
The protected act view suffers from two fundamental flaws. First, despite Dershowitz’s insistence to the contrary, it means that there is very little the president would not have constitutional authority to do. As I explain, the view comes close to collapsing into the royalist view, allowing the president to commit what would otherwise be serious crimes with impunity. Second, sound constitutional interpretation does not support the view’s central claim. Moreover, the legitimate concern that the president’s purposes should not be subjected to constant scrutiny by Congress or the courts can be substantially accommodated without accepting the extreme position that any presidential exercise of power is legally permissible.