A federal appeals court held on Friday that Trump’s claims that he is immune to congressional oversight have no basis in law.

If the Supreme Court does not interfere with this decision, that means the House Oversight Committee will soon gain access to many of Trump’s financial records — potentially including his tax forms.

The case, Trump v. Mazars USA, is an especially significant one because it represents House investigators’ best opportunity to shake records loose from a president who’s offered maximal resistance to any attempt to make him disclose information that he does not want disclosed. The House committee seeks financial records that Trump turned over to his accounting firm, Mazars USA, and the firm has indicated it will comply with the committee’s subpoena if it is ordered to do so.

Trump cannot simply refuse to turn over these records because they aren’t under his control.

Judge David Tatel, a Clinton appointee on the US Court of Appeals for the DC Circuit, wrote the majority opinion in Mazars. And, as his opinion explains, the law governing this case is pretty straightforward. As a series of Supreme Court decisions that stretch back to the 1920s Teapot Dome scandal lay out, Congress has broad authority to conduct investigations so long as those investigations have a “valid legislative purpose.” Such a purpose exists as long as the investigation touches upon a matter “on which legislation could be had.”

In this case, the Oversight Committee began its investigation after “the Office of Government Ethics announced that it had identified an error in one of the several reports that President Trump had filed since he became a presidential candidate in 2015.” Later, Trump’s former lawyer, Michael Cohen, testified to Congress that Trump “‘inflated his total assets when it served his purposes’ in some situations and had ‘deflated his assets’ in others,” thus exacerbating fears that Trump did not comply with federal ethics laws requiring him to disclose his finances.

Among other things, the House says that it wants to conduct an investigation to see if stronger ethics laws are needed to ensure that similar incidents do not arise in the future. That’s a “valid legislative purpose” concerning a matter “on which legislation could be had.” So that should be enough to dispose of this case.

A Trump-appointed judge backed the president

Nevertheless, Trump’s lawyers raise two broad arguments claiming that Trump’s financial documents should be beyond Congress’ reach. The first is that the Oversight Committee’s real purpose is “law enforcement,” not a legislative inquiry, and therefore this investigation is invalid. The second is that a law requiring the president to disclose his finances is unconstitutional and therefore this investigation does not concern a matter on which valid legislation could be had.

The first of these two objections forms the bulk of a dissent by Judge Neomi Rao, a former Trump White House official who Trump placed on the bench earlier this year. Rao argues that the committee “states a double purpose” for its investigation, “to investigate ‘criminal conduct by [President] Trump’ and also to pursue remedial legislation relating to government ethics.” According to Rao, an investigation that touches upon criminal misconduct by a president must arise in the context of an impeachment inquiry, and this investigation is not part of the ongoing impeachment investigation into Trump.

“Because the Constitution provides only one way for Congress to investigate illegal conduct by the President,” Rao claims, the fact that Congress also stated a legislative purpose is irrelevant. No investigation of the president’s allegedly criminal conduct may take place outside of an impeachment inquiry.

The problem with this argument is, as Judge Tatel writes, “no case law supports the dissent.” What the Supreme Court’s decisions actually say is, “Congress’s ‘authority ... to require pertinent disclosures in aid of its own constitutional power is not abridged’ merely ‘because the information sought to be elicited may also be of use’ in criminal prosecutions.”

Tatel also rejects Trump’s second argument, that financial disclosure laws cannot be applied to the present. As the Supreme Court explained in Nixon v. Administrator of General Services (1977), “in determining whether [a law] disrupts the proper balance between the coordinate branches, the proper inquiry focuses on the extent to which it prevents the Executive Branch from accomplishing its constitutionally assigned functions.” Thus, a presidential financial disclosure law would only be unconstitutional if it were somehow so onerous as to prevent the president from fulfilling his “constitutionally assigned functions.”

In Tatel’s words, “we have no basis for concluding that complying with financial disclosure laws” would in any way disrupt those functions.

Now that the DC Circuit has ruled, however, Trump will almost certainly seek a stay of this decision from the Supreme Court. Both Tatel and the other judge in the majority, Judge Patricia Millett, are center-left judges who are well to the left of the current Supreme Court. Judge Rao, meanwhile, is a former law clerk to ultraconservative Justice Clarence Thomas, and her past writings suggest that she is well to the right of the median justice.

We do not yet know whether judges like Chief Justice John Roberts will follow existing precedents that support this investigation. Should Trump receive an emergency stay from the Supreme Court, that could hand him a victory even if he ultimately loses this case on the merits — as the Supreme Court may not decide the case for months or even years.

The fight over whether Trump is immune to investigation, in other words, just entered its end game. The Supreme Court will have to show its hand very soon and that will tell us whether existing law applies to this president.