The president’s argument leads to an absurdity and it therefore must have a flaw, but identifying what precisely is wrong with it is a bit of a puzzle. And it’s worth doing carefully—not simply dismissing the argument because of the clownish aspects of the letter or because of the argument’s audacity.

The key question here is not whether Article II limits the application of the obstruction laws but how much it does so—whether it does so absolutely or only partially. And critically, if it does so only partially, what is the principle under which the obstruction statutes operate against the president?

This is a puzzle over which I have no doubt Mueller’s team has spent a lot of time. It’s a question on which we have relatively little solid law, but Mueller simply could not conduct a protracted obstruction investigation without having developed a theory of whether and how and the president can and cannot violate the obstruction statutes. I don’t know Mueller’s theory. But here is how I would think about the question if I were in his shoes.

Let’s dispense with the easy question first: It is definitely possible for a president to obstruct justice. A president who coaxes a witness to lie, who pays off a witness, who bribes a juror, or who picks up the phone and threatens a federal judge would of course be amenable to criminal prosecution (at least after he leaves office) for obstruction of justice. There would be no plausible defense that he was entitled to do these things because of Article II. This is why both Richard Nixon and Bill Clinton faced plausible criminal jeopardy under the obstruction statutes: In both cases, their obstructive behaviors went well beyond their management of the Executive Branch.

But the allegations against Trump are different, and trickier. They are allegations that his use of his acknowledged Article II powers might constitute an obstruction. The allegations all involve acts—firing people, for example, and supervising investigations and staff—that the Constitution specifically gives the president the power to do. So these allegations raise a different question: Is it possible for a president to obstruct justice in the context of performing his constitutionally assigned role, that is, using only otherwise valid exercises of his constitutional powers?

Before your knee jerks as you exclaim, “Of course!” keep in mind that Congress cannot with a mere criminal statute take away power that the Constitution gives the president. With that principle in mind, it simply has to be the case that Article II, at least to some degree, limits application of the obstruction statutes to otherwise valid presidential actions.

This is a question I considered at some length at Lawfare back in December, and that analysis continues to apply today. The president has the inherent authority to direct the Executive Branch. And to direct sometimes means to hold back, which is to say to obstruct. I don’t doubt that there are many presidential acts that would constitute obstructions of justice if anyone but the president engaged in them but which constitute legitimate exercises of presidential power when the president engages in them.