There are plenty of reasons to think President Donald Trump might try to pardon his way out of special counsel Robert Mueller’s crosshairs.

In March, the New York Times reported that a lawyer for Trump discussed the possibility of pardoning former advisers Paul Manafort and Michael Flynn with their lawyers. The goal, presumably, was to persuade them that they didn’t need to cooperate with Mueller because he’d spare them jail time regardless of whether they were convicted. Trump’s recent pardon of former Bush administration official Scooter Libby, as well as his pardon of Sheriff Joe Arpaio last year, would also show Mueller targets like Manafort that Trump is willing to use his powers to protect his allies.

But if Trump is considering using his pardon power to undercut Mueller’s Russia probe, he might be overlooking a clause in the Constitution that expressly forbids it. This, at least, is the argument Fordham law professor Jed Shugerman made in a column for the Washington Post last month.

According to Shugerman and his co-author, Ethan J. Leib, the Constitution says that the president cannot pardon people for the purpose of self-protection, which means he cannot pardon himself or others in order to shield himself from a criminal investigation. Nor can he use the pardon power to serve his own financial interests.

Their argument is based on a line in the Constitution known as the “take care clause,” which imposes specific obligations on the president. The clause, Shugerman and Leib argue, mandates that the president “execute” the laws in such a way as to advance the public interest and not the president’s private interests.

I reached out to Shugerman to find out more about the take care clause and why he thinks it could stop Trump from abusing his pardon power.

A lightly edited transcript of our conversation follows.

Sean Illing

I’ve heard time and again that the president has virtually unlimited pardoning power. Is that wrong?

Jed Shugerman

I think the key thing is what people mean by the word “virtually.” Yes, people have typically understood the pardon power as “almost unlimited” or “almost absolute,” but it would be inaccurate to say that it’s totally unlimited or totally absolute. The Supreme Court has made fairly clear that Congress cannot limit the pardon power; any limits on the pardon power have to come from the Constitution itself because that’s where the pardon power comes from. So yes, presidential pardon power is quite broad, but there are constitutional limits.

Sean Illing

Let’s talk about the limits outlined in Article II, Section 3 of the Constitution. What’s the clause in there that forbids a president from using pardons to protect himself from an investigation?

Jed Shugerman

This is a famous line of the Constitution that’s called the “take care clause.” It says the president “shall take care that the Laws be faithfully executed.” The key phrase that people have overlooked in that line is what it means to be “faithfully executed.” That same line also comes up in the oath that the president takes; it’s the only oath in the Constitution that is spelled out word for word, and it says the president shall “faithfully execute” the laws. The founders knew what they were doing when they used this language, but over time we’ve missed the original significance of it.

Sean Illing

Why is it significant?

Jed Shugerman

This language comes directly from fiduciary documents from the 17th and 18th centuries. Fiduciary duties still come up today in the context of corporate boards, trusts, wills, and other legal documents that impose obligations on people to act in the best interests of the people they’re serving. A fiduciary duty means you can’t serve your own personal interests over the interests of your client or company or, in the case of the president, your country.

For example, the executor of a will or estate cannot line his own pockets to the detriment of the estate or the beneficiaries. A CEO or a corporate board cannot embezzle money from the corporation to the detriment of corporate interests. So when the framers of the Constitution adopted this language from fiduciary law, they were drawing from those core legal principles.

Sean Illing

So in the same way a lawyer or a CEO must act in the best interests of her client or company, a president is compelled by the Constitution to execute the laws in such a way as to protect the best interests of the people?

Jed Shugerman

That’s absolutely right.

Sean Illing

How difficult might it be to make a legal argument that the president was acting solely in his own “self-interest”? If the president pardons himself, that seems pretty clear-cut. But if he’s pardoning other people, it may not be so simple even if it’s more or less apparent that he’s acting out of self-interest.

Jed Shugerman

This is the million-dollar question. So let’s start with the core question about whether a president can pardon himself. Clearly, a self-pardon is a breach of fiduciary duty because it’s manifestly self-interested. But if a president managed to do this, the following administration could try to prosecute the president, which would force a court to examine that president’s self-pardon and decide whether or not it was invalid on the grounds that it violated his fiduciary duty to serve the best interests of the people over himself. Similarly, if a president pardons co-conspirators in a crime, the next administration could challenge those pardons in court by claiming they were invalid for the same reasons.

Sean Illing

All of this makes sense to me, and it’s certainly a plausible reading of the Constitution, but has this ever been tested in court?

Jed Shugerman

No. This is an argument that is based on historical research that unearths the background of the Constitution’s text, but that background has been lost over time as we’ve started to talk differently about the Constitution. But the argument I’m making is perfectly in line with the language and intent of the Constitution.

Sean Illing

If we accept the claim that the president has an obligation to act for the right reasons, which is to say in the interests of the people, and not of himself, he seems to have already crossed this line by firing Comey because of the Russia investigation (which he actually admitted). We also know that Trump’s personal lawyer floated the possibility of pardoning Manafort and Flynn, presumably to influence their decisions to cooperate with Mueller.

Jed Shugerman

I want to repeat something you said, which is exactly right. The faithful execution language of the Constitution mandates that presidents and other officials must act for the right reasons and not for self-interest against the public interest. This also applies to the firing question.

Most people don’t realize that the Constitution never explicitly mentions the power to fire. This was a gap in the Constitution that had to get worked out by the first Congress. So we’re making the argument that the Constitution’s language regarding faithful execution has to be considered when we have only an implicit understanding that the president has the power to fire.

So the way this would work with, say, Mueller, is that Mueller and Deputy Attorney General Rod Rosenstein could go to a court and get an injunction to prevent their firing by the president based on this argument about faithless execution. Comey could have done that too, but that ship has already sailed. But I think someone like Mueller could argue that he’s conducting a legitimate criminal investigation and therefore should be protected from being fired by the subject of that investigation.

Sean Illing

Do you think this argument will be tested in court?

Jed Shugerman

No, I don’t. Mainly because Mueller has been careful and strategic in the ways that he’s protected the investigation even in the event that he’s fired. For example, the recent Michael Cohen raid was handed over to the Southern District of New York, so even if Mueller is fired, there’s now a basis for another office to continue the investigation and perhaps to broaden it to state-level crimes, which are shielded from presidential pardons. So there are enough failsafes against his firing that I doubt he’d ever need to test this argument in court.