The effect of the FBI director’s dismissal on the constitutional order, if there is to be any, probably depends upon whether the Constitution’s system of checks and balances will work again to take the nation through the disturbance. It was the genius of the Founders, especially James Madison, that saw ultimate stability in the contending forces of the government’s centers of power. . . .Like I mentioned in class yesterday, the ability to stop an out-of-control President most surely exits in the Constitution. The question is whether there will be the political will do so.
Noah Feldman has a piece at Bloomberg that also concludes the President's actions have not created a constitutional crisis but they do violate long-standing political norms:
It’s not a constitutional crisis. Technically, President Donald Trump was within his constitutional rights Tuesday when he fired FBI Director James Comey. The Federal Bureau of Investigation is part of the executive branch, not an independent agency. But the firing did violate a powerful unwritten norm: that the director serves a 10-year, nonrenewable term and is fired only for good cause.It should be noted that supporters of the President claim that he had good reason to fire the Director. But should it come out that the real reason for the firing was to stop an investigation into members of the President's inner circle or even into the President himself, I can almost guarantee that the constitutional controls that we discussed in class will kick in.