The Supreme Court of the United States handed President Trump one partial win and one loss on matters relating to subpoenas for his tax records, but it rejected the president's argument that he has broad immunity from investigations while in office.

In one group of cases, Trump v Mazars, the court sided with the president, for now, vacating decisions that upheld congressional subpoenas and remanding the cases back to the lower courts. The cases involved congressional subpoenas from three different House committees all seeking the president's tax records from the firm Mazars USA. The committees argued that the financial information sought would help guide legislative reform in areas ranging from money laundering and terrorism to foreign involvement in U.S. elections. The White House argued that such requests violated the separation of powers, saying there was no legitimate legislative purpose to them. House Democrats, however, argued this was not a separation of powers issue because they were seeking personal records from a third party, which they said was implicitly recognized by the president as he sued in his personal capacity. While the lower courts had agreed with this position, the Supreme Court did not.

The court, in a 7-2 opinion written by Chief Justice John Roberts Jr., disagreed with the administration's position that the the House had to establish a "demonstrated, specific need” on par with the Watergate special prosecutor needing the Nixon tapes, saying that this standard was too strict. "Unlike the cases before us, [the Watergate cases] involved Oval Office communications over which the President asserted executive privilege," the court found. "We decline to transplant that protection root and branch to cases involving nonprivileged, private information, which by definition does not implicate sensitive Executive Branch deliberations."

However, the court also faulted Congress' argument that the case does not involve separation of powers at all.  While Congress cited numerous precedents involving investigations of other papers, the court said that none of them specifically involve those belonging to the president. While lower courts applied rules as if he were any other private citizen, the opinion essentially said that the president is not just any other private citizen due to the intentionally adversarial relationship between the executive and legislative branches.

Roberts said that, despite what Congress argued and the lower courts agreed upon, it is obvious that this is not about a run of the mill legislative investigation but "a clash between rival branches of the government over records of intense political interest for all involved." Further, he said that "the interbranch conflict here does not vanish simply because the subpoenas seek personal papers or because the President sued in his personal capacity," nor is it mitigated by the information being sought from a third party as they are still seeking presidential information. 

Given this conclusion, the Supreme Court determined that the lower courts did not adequately consider separation of powers violations, and so it vacated their decisions and remanded the cases "for further proceedings consistent with this opinion." The high court said that, upon remand, the lower courts should determine whether the president needs to be involved at all for the legislative purpose in question; insist on a subpoena no broader than reasonably necessary to support Congress’s legislative objective; be attentive to the nature of the evidence offered by Congress to establish that a subpoena advances a valid legislative purpose; and be careful to assess the burdens imposed on the president by a subpoena.

Generally, the court said the president should not be used as a specific case study for broad legislative goals when Congress can get the information  it needs from other sources. The opinion differentiated these cases from criminal proceedings, where a failure to disclose all the facts necessary to the case would undermine the integrity of the judicial system. It is this difference that led the court, in the other case, to side against the White House.

The case Trump v. Vance, involved a subpoena not from a congressional committee but from the New York County District Attorney's office. The New York D.A. had demanded the president's financial information as part of an investigation into possible financial crimes involving payments made to buy the silence of an adult film star who supposedly had an affair with the president, specifically whether any senior executives at his company filed false business records about the hush money.

The 7-2 opinion, also written by Roberts, noted that there is a wealth of precedent for presidents testifying or producing documents in criminal proceedings when called upon by federal courts, going all the way back to Thomas Jefferson. That the president must submit to subpoenas in a criminal investigation, said the court, has been long established and reaffirmed multiple times over two centuries. The president's attorneys did not dispute this precedent but argued that he has blanket immunity from any state criminal subpoena, as complying with it would excessively interfere with his functions as the executive. The Supreme Court dismissed this stance out of hand, however, saying that President Bill Clinton tried the same argument in the Paula Jones case and failed. If it didn't work then, said Roberts, it won't work now. Just being distracted is not sufficient cause to invalidate the subpoena, especially because the president conceded that grand juries do indeed have the right to investigate a sitting president.

The court further said that the president's argument that compelling him to comply with state subpoenas would subject him to harassment doesn't work either, once again because President Bill Clinton tried the same argument before and lost. As articulated in that case, Roberts noted that courts have ample tools to discourage baseless lawsuits, and so this concern is not a serious one. He further added that grand juries are prohibited from engaging in arbitrary fishing expeditions already, and that these protections apply with special force when it comes to the president.

The court, however, said that such a standard would extend the protections that currently apply to official papers to personal ones, which would go against precedent set literally centuries ago. It also said that there is no legal basis for a double standard in which a federal subpoena is warranted when the information is material but a state subpoena must seek information that is essential. Finally, applying the threshold that the president wanted would hobble the ability of grand juries to acquire "all information that might possibly bear on its investigation." States, he said, would be deprived of investigative leads that further evidence might yield and, furthermore, "it could prejudice the innocent by depriving the grand jury of exculpatory evidence."

Thomas and Alito also dissented in the case involving criminal subpoenas. Thomas, in his dissent, said that while the president does not have blanket immunity from the issuance of subpoenas, he does have immunity from their enforcement. If the president can show that his duties "as chief magistrate demand his whole time for national objects," then he is entitled to relief from enforcement of the subpoena. Alito, in his dissent, said that the country has long understood a need to shield the presidency from interference from the states. While he conceded that sometimes a subpoena is necessary, he said that the legal test needs to account for "the need to prevent interference with a President’s discharge of the responsibilities of the office." As one of many examples he raised, he asked whether, according to the majority's view, the president under criminal subpoena would need to ask the court to attend the G-7 conference. He asserted that the majority opinion did not provide any protections for the presidency.