You might think that the Supreme Court case regarding President Donald Trump’s tax returns is about him, or least about the power of the presidency. It isn’t. As Tuesday’s livestreamed oral arguments made clear, this is a case about Congress — and whether its oversight authority will be stripped away by an activist Supreme Court.

The Constitution gives Congress “all legislative powers herein granted.” The text of the Constitution doesn’t speak of “legislative oversight” because the phrase itself wasn’t used until the 1830s, and didn’t become widespread until after World War II.

But make no mistake, Congress has exercised what we call legislative oversight from the very beginning. The way Congress did so was no different from the way it does now: The legislators held hearings, asked questions and subpoenaed documents.

The tradition is robust. Today Congress holds a range of different kinds of hearings, including hearings labeled legislative, oversight, investigative, confirmation, ratification and impeachment. All of them include oversight of government in one way or another.

Constitutionally, it hasn’t been considered a problem that this oversight authority derives from a constitutional grant of legislative power. After all, to decide what legislation to adopt, Congress first needs to understand what is needed. Oversight is an inextricable part of the process of figuring out what works in the country and what doesn’t. It isn’t meaningfully possible to differentiate oversight from the rest of the legislative process.

Existing Supreme Court doctrine effectively recognizes this. In the leading case, Wilkinson v. United States, which involved questions about membership in the Communist Party put to a witness under subpoena by a House subcommittee, the court said the subpoena would be valid provided five conditions were met: The investigation must be authorized by Congress, the committee must be pursuing a “valid legislative purpose,” the question must be pertinent to the investigation, the questioned must be told that it was pertinent, and the question must not violate his fundamental constitutional rights (in that case to free speech and association).

This test gives tremendous leeway to Congress in performing oversight. Provided Congress authorizes the inquiry, which is pretty clearly the case regarding Trump’s tax returns, all that’s required is that the subpoena be pertinent to a valid legislative purpose and not violate the target’s constitutional rights.

Trump’s tax returns certainly fit the bill. Congress is engaging in oversight when it demands Trump’s pre-presidential tax returns from his accountants. That oversight is not rationally separable from the possibility of legislation. Congress could, if it chose, adopt legislation requiring presidential candidates to disclose their tax returns. In fact, Congress could even require that all of our tax returns be made public.

What’s happening in the case before the Supreme Court is that Trump’s personal lawyers, and to a degree the office of the solicitor general, are trying to radically limit Congress’s oversight power. The way they’re doing this is to say that Congress has to provide a highly specific legislative purpose in order to issue a subpoena — even, perhaps, specific proposed laws.

In other words, they are trying to turn the phrase “valid legislative purpose” on its head. Instead of the phrase being broad and permissive of congressional authority to subpoena, they want to make the phrase narrow and restrictive of congressional power.

In the process, they want to break the connective link between oversight and legislation. According to their theory, simple oversight doesn’t count as a valid legislative purpose — despite the historical and logical connection between the two.

Reading the tea leaves after the oral argument, I think the justices are unlikely to rule entirely in favor of Trump. At least some of the conservatives surely realize that too restrictive a reading of “valid legislative purpose” would not merely hamstring congressional oversight, but cripple it.

Justice Neil Gorsuch asked why it wouldn’t make sense to defer to Congress regarding its determination of a substantial legislative need. And Justice Brett Kavanaugh, who worked on the Whitewater investigation into President Bill Clinton’s finances, asked a question in which he pointed out that the Whitewater subpoenas were a precedent in favor of Congress. He could, of course, now repudiate that instance, which was not litigated to the Supreme Court — but that would require drawing attention to his own flip-flop on that case.

On the other hand, Chief Justice John Roberts, whose vote is certainly crucial, asked the lawyers for Congress whether they could articulate any limiting principle for what should count as a valid legislative purpose.

The right answer is that a valid legislative purpose encompasses anything that Congress says it is, provided Congress isn’t demonstrably engaged in intimidation or abuse and hasn’t violated anyone’s constitutional rights. Any weaker answer is an invitation to the Supreme Court to disastrously weaken Congress’s oversight capacities.

Trump’s lawyers naturally want the justices to pay attention to the fact that Trump is now the president, in order to make the case look like one in which the interests of the legislative branch should be weighed against the interests of the executive. But the tax returns predate Trump’s presidency. Nothing about producing them will interfere with the exercise of his office. And the Supreme Court already held nearly a quarter of a century ago in Clinton v. Jones that the president isn’t above the law. If he can be sued civilly in his personal capacity while in office for conduct occurring before he became president, his tax returns can certainly be made public.

Ultimately, this case is about congressional oversight. In a divided government, that’s just about the most important function that Congress has. The court should preserve it, not kill it.


Noah Feldman is a Bloomberg Opinion columnist and host of the podcast “Deep Background.” He is a professor of law at Harvard University and was a clerk to U.S. Supreme Court Justice David Souter. His books include “The Three Lives of James Madison: Genius, Partisan, President.”