Noah Feldman is the Felix Frankfurter Professor at Harvard Law School and a columnist for Bloomberg View. His most recent book is The Three Lives of James Madison: Genius, Partisan, President. (May 2018)
The investigation of Michael Cohen, a lawyer and sometime fixer for Donald Trump, marks the start of a new phase in the unraveling of Trump’s presidency. Until now, the only Justice Department investigation of Trump has been conducted by special counsel Robert Mueller. Mueller’s appointment letter authorizes him to investigate Russian interference in the 2016 election and crimes arising from it. Any wrongdoing that is not connected to this interference arguably falls outside Mueller’s scope. In contrast, the Cohen investigation is taking place not under Mueller, but under the authority of the US attorney for the Southern District of New York. The Southern District is not restricted by any appointment letter, and its career attorneys have a mandate to uncover any criminal activity within their jurisdiction, whenever it may have occurred and for whatever purpose.
Because it has been used so rarely, and because it is a power entrusted to Congress, not the courts, impeachment as a legal process is poorly understood. There are no judicial opinions that create precedents for how and when to proceed with it. Past cases are subject to competing and often contradictory interpretations. Some might even be tempted to argue that because impeachment is ultimately political, it cannot be considered in legal terms at all. That extreme view cannot be right. Impeachment must be a legal procedure because it derives from specific constitutional directives.
Twenty-odd years ago, I went to the office of the immensely distinguished Harvard historian Bernard Bailyn to ask about objectivity in historical writing. Tolerating my sophomoric questions (in my defense, I was in fact a sophomore), the great man explained that historiography had three phases: heroic history, in which individuals …