The Constitution creates three coequal branches of government, and no branch may exercise its authority in a manner that would negate or fundamentally undercut the power of another. The power to appoint and remove high-level executive-branch officers, such as the FBI director, is a core aspect of the president’s executive authority. It is the principal means by which a president disciplines the exercise of the executive power the Constitution vests in him.
The same is true of Mr. Trump’s request, as purported by Mr. Comey: “I hope you can see your way clear … to letting Flynn go.” The FBI director wields core presidential powers when conducting an investigation, and the president is entirely within his rights to inquire about, and to direct, such investigations. The director is free to ignore the president’s inquiries or directions and risk dismissal, or to resign if he believes the president is wrong. Such officials serve at the president’s pleasure and have no right to be free of such dilemmas.