Barely six months in office, President Donald Trump has unleashed more unresolved constitutional questions than any president in history.

Can Trump be indicted for federal crimes such as obstruction of justice? A federal investigation of Trump by Special Counsel Robert Mueller is considering exactly that question, but the Constitution does not give a definitive answer.

Short of impeachment, can Trump be removed from office? The Constitution’s 25th Amendment says he can be if he is “unable to discharge the powers and duties of his office.” But what if he is perfectly capable of discharging his duties, even if he is doing it corruptly? The Constitution does not provide a clear answer. Can Trump receive “emoluments” from foreign governments? Article II, section 1 of the Constitution says he cannot, but what exactly is an emolument? Does Trump’s retention of his business empire, which he refuses to disgorge, prohibit his continued receipt of financial gain from foreign governments, as a recent lawsuit by attorney generals from the District of Columbia and Maryland allege?

And finally, can Trump issue pardons, even to himself, in order to undermine Mueller’s investigation? The question has never before been squarely considered. To be sure, Article II section 2 of the Constitution gives a president extremely broad pardoning power, and presidents historically have used that power broadly, without needing to justify its use. But can a president’s grant of pardons be so extreme, and so detrimental to the integrity of the Republic as to constitute by itself an obstruction of justice? Indeed, that this question is being raised is a sign of how low this country has sunk since Trump became president.

The Constitution provides no explicit answer as to the scope of the president’s pardon power. Courts and commentators have assumed that a president’s power to pardon anyone for a federal crime is virtually unlimited, although the question of a president’s power to pardon himself has never been seriously discussed.

The meaning and scope of the Constitution’s pardon power can be gleaned from history, precedent, and logic. First, pardons have always been granted to other persons or groups with the purpose to promote domestic tranquility and temper the harshness of the criminal law. No president has ever pardon himself. Second, a clearly textual constitutional limitation is that the president’s pardon power does not override the constitution’s impeachment process. So, for example, Congress could impeach Trump if he used his power to pardon cronies and family members. And third, a pardon may not be used to supplant criminal charges by a state. A state attorney general or a local district attorney could decide to bring state criminal charges against Trump or his associates— say, for conspiracy, bribery, obstruction of justice, and fraud.

All commentators appear to have conceded Trump’s power to pardon persons who are being investigated, charged, or convicted of federal crimes. On Twitter, Trump said he had “complete pardon power” and his inner circle is reportedly scheming to interfere with Mueller’s investigation, including research on the extent of Trump’s pardon power and whether he has the constitutional power to pardon himself.

The question is whether Trump’s granting pardons for a corrupt purpose, like obstructing Mueller’s investigation, would be valid and whether the pardons could be reviewed by courts.

Procedurally, whenever a president issues a pardon to abort a criminal conviction, terminate criminal charges, or even prevent prospectively criminal charges from ever being brought, a judge typically has to issue a formal order dismissing the matter. The prosecutor certainly could condemn the pardon publicly as a “cover-up,” as Independent Counsel Lawrence Walsh did in 1992 after the first President Bush pardoned six persons, including former defense Secretary Caspar Weinberger, in the Iran-contra scandal. But Walsh never sought review by a court of the validity of the pardons as he theoretically could have done. He could have argued that the pardons were illegitimate, were granted in bad faith, and that the president was trying to shield persons from criminal accountability for political reasons and indeed may himself have been involved in a conspiracy to thwart the federal investigation. And presumably if Walsh lost he could have appealed to a higher court, even the U.S. Supreme Court. Whether the courts would have considered his appeal is unclear.

But the history of the pardon power suggests that Walsh may have a plausible argument. Indeed, the fact that the pardon power has never been seriously challenged as being corruptly exercised is curious. Historically, the Constitution’s pardon power, promoted mostly by Alexander Hamilton, was seen as a limited opportunity to afford a president a power that would enhance his ability to govern responsibly by controlling insurgencies and restoring domestic tranquility. Thus, in No. 74 of his Federalist Papers, Hamilton argued that “humanity and good policy” should be used to temper justice with mercy and mitigate the harsh justice of the criminal code. The pardon power should be used, he argued, to provide “exceptions in favor of unfortunate guilt.”

In keeping with Hamilton’s understanding, President George Washington used it to forgive revolting farmers during the Whiskey Rebellion. President John Adams used it to pardon soldiers who had deserted during the Revolutionary War. President Jimmy Carter used it to redeem young Americans who dodged the draft during the Vietnam War. And many other presidents have used the pardon power for benign, and sometimes politically suspect reasons, to pardon friends, donors, and even a former president, Richard Nixon.

Supreme Court precedents do not provide as firm a foundation for the use of the pardon power as Trump would like to believe. The decision affirming its scope—Ex Parte Garland in 1866—was a post-Civil War decision that focused less on the scope of the pardon power than on whether it could be used to restore offices or property forfeited. Read in conjunction with two other post-Civil War decisions of dubious precedential value—Ex Parte McCardle and Ex Parte Milligan—Garland is arguably a tenuous foundation to support Trump’s grandiose view of his pardon power.

In fact, at the time of the framing of the Constitution it was not seriously contemplated that a president would ever use the pardon power for a corrupt purpose, and it would have seemed to the Framers nonsensical that a president would try to pardon himself. Chief Justice John Marshall saw the pardon power as emanating from a responsible president and bestowed upon a worthy recipient, as an “act of grace which exempts the individual on whom it is bestowed from the punishment the law inflicts.” James Wilson, one of the key Framers at the Constitutional Convention, saw the pardon power in utilitarian terms, as a way obtaining the testimony of accomplices. Justice Oliver Wendell Holmes saw the pardon power not as a private act of grace but as part of our constitutional scheme. To these distinguished commentators, the Constitution embodies a carefully-wrought scheme of checks and balances, represents a charter to protect the rule of law, and is a document that creates a government of limited powers. The suggestion that a president has the power to pardon to undermine the rule of law and the integrity of a democracy by granting pardons corruptly would have seemed to the Framers entirely inconsistent with the purpose of our Constitution.

Moreover, as a matter of logic, if a president could grant pardons to prevent an investigation into whether a foreign government, aided by U.S. accomplices, conspired to corrupt this country’s democratic process, he would be destroying the historic foundation upon which the rule of law is built: the idea that no person should be a judge in his own cause. This famous axiom clearly applies if a president is able to pardon cronies, family members, and even himself. Interpreting the Constitution to condone this perverse use of power would be to announce that we are not a nation of laws, and that the president is above the law.

The Constitution does not explicitly preclude the possibility that Trump might actually try to use the pardon power in an effort to obstruct justice. He has done so many bizarre things, and engaged in such blatantly unethical behavior, that nothing he does would seem beyond the pale. But any suggestion that the Constitution should be interpreted in a way that allows a president to issue pardons to undermine an investigation into our democratic process would have seemed to the Framers who wrote our constitution and created our government to be farfetched, fantastic, and absurd. In such a case judicial intervention would seem completely appropriate. Such abuse of power would be seen as so far beyond the scope of a president’s constitutional authority, and the impact to our democracy so great, as to merit judicial review despite prudential concerns that would ordinarily counsel silence.