We’re about to hear a lot about “executive privilege,” and a lot of it will probably be wrong.

The president’s position—as of this writing—is that he would be very happy to have former National Security Adviser John Bolton, Secretary of State Mike Pompeo, acting White House Chief of Staff Mick Mulvaney and former Energy Secretary Rick Perry all testify at his impeachment trial, which begins today. But, out of an abundance of concern for the institutional integrity of the presidency, he reluctantly will have to invoke executive privilege and forbid them from talking.

He was recently asked about it by Fox News’ Laura Ingraham. “You can’t be in the White House as president—future, I’m talking about future, any future presidents—and have a security adviser, anybody having to do with security, and legal, and other things,” the president said.

“Are you going to invoke executive privilege?” Ingraham asked, seeking clarity.

“Well I think you have to for the sake of the office,” Trump replied.

The Founding Father of executive privilege.

While cynics might suspect that Trump’s invocation of executive privilege is motivated by narrower and more personal concerns, it’s not an illegitimate argument. All presidents have worked assiduously to protect executive privilege, starting with George Washington.

In 1796, the capital was wracked by its first major fight between Congress and the White House. George Washington had worked out a trade agreement with the British, known as the Jay Treaty. This made the French—our allies during the recent unpleasantness with England—quite displeased, especially because the French were once again at war with the British. The French had many sympathizers—and the Brits had many detractors—in the House. Members of Congress demanded that the president turn over all of the paperwork that went into the treaty: notes from meetings, letters etc.

Washington refused. In a letter, widely considered the first instance of a president invoking executive privilege, Washington wrote: “The nature of foreign negotiations requires caution, and their success must often depend on secrecy.” He continued: “To admit, then, a right in the House of Representatives to demand and to have as a matter of course all the papers respecting a negotiation with a foreign power would be to establish a dangerous precedent.”

Ever since, executive privilege has been claimed by every president, at least in theory, and recognized by numerous courts, even if case law on the subject is more scant than you might think.

What is executive privilege?

In short, it’s the president’s “right” to keep certain communications from Congress or the public. I use quotation marks around “right” because it is not an absolute right, but a presumption of deference to the president. The kinds of communications that executive privilege is intended to cover are those that are central to his core constitutional functions and duties, such as discussions with foreign leaders, advice from his national security team, etc. Imagine the chilling effect if Congress—and by implication the media—could discover politically controversial advice from senior advisers. It wouldn’t take long for advisers to start policing what they say. Similarly, if foreign leaders could not trust that their conversations with the U.S. president would remain confidential, frank exchanges of views would be nearly impossible.

Executive privilege is a vital presidential shield—and sometimes sword—in battles with Congress and the courts over presidential communications and the inner workings of administrations. Its advocates argue that it flows from the structure of the Constitution and the separation of powers. The Supreme Court has recognized that, in judicial proceedings such as civil and criminal trials, the president cannot be treated like any other ordinary Joe because the president is both a person and a branch of the government. In the words of Chief Justice John Marshall when prosecutors sought documents from the Jefferson administration in Aaron Burr’s treason trial, “In no case of this kind would a court be required to proceed against the president as against an ordinary individual.”

The court has long recognized, then, that “[t]he expectation of a President to the confidentiality of his conversations and correspondence ... has all the values to which we accord deference for the privacy of all citizens and, added to those values, is the necessity for protection of the public interest in candid, objective, and even blunt or harsh opinions in Presidential decisionmaking.”

The court found in United States v. Nixon, one of the many cases involving claims of privilege in Watergate, that presidents and their advisers must not live in a fishbowl, lest they pull their punches in addressing the critical issues of the day for fear of public disclosure of candid and sometimes uncomfortable advice: “A President and those who assist him must be free to explore alternatives in the process of shaping policies and making decisions and to do so in a way many would be unwilling to express except privately.”

Thus, Congress (or the courts for that matter) may not demand core presidential communications simply for the sake of morbid political curiosity. As Washington argued, they need a good reason, even a damned good reason. And we’ll come back to George Washington in a moment.

The limits of privilege.

None of this means, however, that the president has an absolute right to shield his confidential communications from public scrutiny. Indeed, the Supreme Court has rejected an absolute privilege. Instead, the court concluded that there is a “presumptive privilege” for presidential communications. That presumption—and the constitutional concerns underlying it—are strong enough to prevent Congress from subjecting the president’s core deliberations to sunshine laws, like the Freedom of Information Act and similar “right to know” laws. Those laws are often interpreted by the courts to preserve legitimate claims of presidential confidentiality. The privilege is strongest in areas where confidentiality is vital for the president’s ability to deal with core national security, diplomatic, and military concerns. In those areas, the Supreme Court has afforded the president’s need for confidentiality the “utmost deference,” according to Nixon.

As a practical matter, executive privilege often works less as a legal bright line and more like one of the “gentleman’s agreements” that have evolved over time to make government work by filling in some of the constitutional blanks left by the founders. For instance, there’s nothing in the Constitution that says the Justice Department can’t subpoena journalists’ notes and papers while conducting a criminal investigation, but courts, and prosecutors generally recognize that doing so should be a last resort, given the special role that a free press plays in our system. Executive privilege rests on this kind of good faith understanding between the institutional players, which is why presidents take care not to abuse it, lest Congress or the courts curtail it in response. Disputes between Congress and the executive branch are usually worked out to avoid running into the problem of bad cases making for bad law.

Before we continue, there’s another point that needs to be made. In interviews President Trump often makes it sound like he can forbid current and former members of his Cabinet from testifying before Congress. That’s not quite right. It is true that he can tell his acting chief of staff Mick Mulvaney not to testify. But Mulvaney would be perfectly free to defy the president if he wanted to. And so long as Mulvaney did not divulge state secrets or the like, the worst the president could do is fire him. As for John Bolton, he’s already been fired. So if Bolton opted to testify, the only thing Trump could do to him is be mean(er) to him on Twitter. Piercing executive privilege (without divulging classified material) is not a criminal, or even civil, offense, even if the president orders you not to.

So, what are the circumstances when the president’s interest in confidentiality is outweighed by the need for disclosure? When Congress or the courts are fulfilling their own core constitutional functions.

Which brings us back to George Washington. Recall that Washington insisted the House had no business looking at confidential documents pertaining to the Jay Treaty. But, ever the constitutional stickler, Washington let the Senate see them. Washington recognized the Senate’s right to the materials due to that chamber’s constitutional role in ratifying treaties.

More relevant to current events, Washington conceded another point: The House would have every right to look at the documents if it were conducting an impeachment inquiry. “It does not occur,” he wrote, “that the inspection of the papers asked for can be relative to any purpose under the cognizance of the House of Representatives except that of an impeachment, which the resolution has not expressed.”

There was unanimity in Washington’s Cabinet on this point. That’s kind of a big deal given that the Washington administration was literally chock-a-block with Founding Fathers, as anyone who has seen Hamilton the musical would recall. Treasury Secretary Oliver Wolcott (a signatory of the Declaration of Independence) wrote that “when an Impeachment is proposed & a formal enquiry instituted,” Congress can get whatever it asks for.

In other words, executive privilege had its limits, and impeachment was definitely one of them. As law professors Jean Galbraith and Michel Paradis note in this useful primer, “If a president’s diplomatic communications might have evidence of impeachable conduct, Congress is entitled to see them.”

The president’s legal team is correct when they say that the president’s power and privileges are strongest in matters related to foreign policy. But the best response to this is that Congress’ ability to overpower presidential privilege is strongest when it’s performing a core constitutional function in general and impeachment in particular. Again, as a general rule, powers enunciated in the Constitution outrank powers merely implied by the Constitution.

Case law is more complicated—because, lawyers—but ultimately comes to a similar conclusion: Core constitutional functions and interests can trump executive privilege.In United States v. Nixon, the court held that the president could be compelled to provide documents (in the form of Oval Office tapes and similar records) in grand jury investigations of Watergate conspirators. The substantial constitutional interests in the proper functioning of the criminal justice system were held sufficient to overcome the president’s interests in confidential communications, at least where the communications did not implicate national security and similarly sensitive communications. President Nixon was required to turn over the tapes. He resigned soon thereafter.

What now?

It’s funny given all of this setup, but neither historical precedent nor case law really have nearly as much bearing on what happens in the Senate than you might think if you listened only to legal pundits—or for that matter the Democratic impeachment managers or the president’s legal team. The Senate can pretty much do what it wants. More on that in a moment.

But, since politicians and pundits alike tend to think that the impeachment process is supposed to be more legalistic than the Founders intended, both sides will likely be invoking legal arguments to bolster their cases. That might not be good news for the president.

Indeed, the president undermined his own case to some extent when he ordered the release of the rough transcript of his phone call with the president of Ukraine. Whether that call was “perfect,” as the president insists, or the smoking gun equivalent to the Nixon tapes as many critics contend, is beside the point. If communications with a foreign leader are not important enough to protect from disclosure, the president’s interest in protecting secondary conversations about those communications is not nearly as compelling as it might otherwise seem.

Again, in a legal proceeding, a president’s privilege claim can be outweighed when Congress can demonstrate a specific need for testimony in carrying out a constitutional function. Given that grand jury proceedings in the Nixon case met that test, it would be difficult to argue that the Senate’s trial of the articles of Impeachment is not at least as serious a constitutional function. Indeed, a recent DoJ opinion concedes as much. Despite the seeming frivolity of this particular impeachment process at times, the impeachment and trial of a president is perhaps the most serious constitutional function that Congress performs, short of declaring war.

But, if a judge were hearing a case over whether or not John Bolton could be forced to testify, recognizing the seriousness of impeachment would be just part of the calculation. A judge would also ask, how much does the Senate need this information to try Donald Trump? Is it worth piercing the privilege if there’s ample evidence elsewhere? Imagine if Trump confessed on national TV. You wouldn’t need to drag Bolton into the dock to confirm what the president already admitted.

So here’s the key point: Politically speaking, with a Republican-controlled Senate, these questions as they pertain to this impeachment trial will not be put before the Supreme Court, or any court. Questions about additional evidence and testimony will be decided by a simple majority of the Senate. Chief Justice Roberts may be presiding at the trial, but he will not actually be serving as a judge. And even if he tried to, he could still be overruled by a simple majority of the Senate. And it is highly unlikely that Democrats will convince four Republican senators to sue a Republican president—even Mitt Romney has his limits after all.

So, it’s up to the 100 senators. They can recognize all or some of Trump’s privilege claims, whether or not those claims would stand up in a court of law. A strong case could be made that the Senate is, of course, entitled to any testimony that it deems necessary to perform its constitutional duty—as our friends at the Lawfare blog suggest.

But how compelling is the Senate’s need here? Is the testimony going to tell them something new or is it just more of the same? That is something that may be impossible to know until Bolton—or anyone else—actually testifies. As a political matter, the House’s rush to judgment on impeachment may undermine the case for compelling the testimony of witnesses like Bolton, who were not similarly required to testify in the House before it issued its articles of Impeachment. If it was not important enough to require the testimony to support the House’s decision to impeach, what is the compelling reason to require that testimony now? But again, this is not an issue of criminal law or even law generally, but a political calculation that will have relevance even if the senators took an oath to deliver “impartial justice.” No doubt some Republican senators will look for reasons they cannot hear new evidence—however much they claim to want to hear it—because of some constitutional or legal requirements. There are none. If 51 senators decide that they need to hear a witness and then follow through by actually demanding the witness appear, there is no appeal of that decision. No court will overrule the Senate on something like this.

The functions of each chamber of Congress in this process are different, and the Senate may independently and legitimately determine to cast a broader net than the House. TV lawyers of the left and the right who tell you that the Senate can’t do this or has to do that are almost always going to be guilty of special pleading. They will talk gravely about upholding or breaking “precedents.” And sometimes they will have a point. But with a track record of exactly two previous presidential impeachment trials, precedents are bound to be created and destroyed no matter what. The point is, each Senate can create pretty much any new precedents it wants.

The time for hammering out these privilege claims probably expired when the House opted not to go to court to force Bolton & Co. to testify.

And that’s the danger here for supporters of a robust interpretation of executive privilege. If Trump sticks to his guns by claiming blanket executive privilege because the whole impeachment effort is a “hoax” and a “witch hunt,” the Senate could deal a devastating blow to the entirety of the gentleman’s agreement and set a precedent that will undermine future claims. That would be a strange argument for even the most ardent supporters of the president to make: We must ignore evidence in an impeachment trial to preserve the ability of future presidents to hide impeachable offenses.

It would be a strange irony—and a sign of further degeneration of the legislative branch—if the Senate ultimately opted not to call witnesses in order to save the executive branch’s ability to deny it information it is constitutionally entitled to get.

But stranger things have happened.

Photograph of Donald Trump by Saul Loeb/AFP via Getty Images.