Is There Any Limit on the Congressional Subpoena Power?

There was a potentially pivotal exchange in today's Supreme Court oral argument over the House subpoenas seeking the President's financial records.

A pivotal moment during oral argument in United States v. Lopez came when the Solicitor General was asked whether, on the government's theory, there was any activity beyond the scope of Congress' power to regulate "commerce . . . among the several states." The Solicitor General had no answer, and the need for an outer limit on the scope of legislative power was a key element in Chief Justice Rehnquist's Lopez opinion. [Audio of the exchange may be heard here.]

Several years later, in Morrison v. United States, the Solicitor General was asked the same question. Again the SG came up short. He was only able to cite the law invalidated in Lopez as an example of a law that would exceed the scope of legislative power. And again, Chief Justice Rehnquist wrote an opinion striking down the law in question emphasizing the need for an outer limit on legislative power.

The question in Lopez may have been a surprise, for the Supreme Court had not invalidated a law for exceeding the scope of Congress' enumerated powers in decades. In Morrison, however, it was obvious this question would be asked, and that it would matter to five justices. Accordingly, in NFIB v. Sebelius, the question of whether the individual mandate could be upheld as an exercise of the Commerce Power without obliterating the principle of limited and enumerate powers, was raised repeatedly (and ultimately figured in the Court's rejection of the Commerce Power theory for the mandate's constitutionality).

In today's oral argument in Trump v. Mazars, the attorney for the House of Representatives was asked (repeatedly) to identify a limit on Congress' subpoena power, and he came up empty. He was unable to identify any information about the President that Congress could not demand.

This was a predictable question, and the inability to provide an answer seems like an unforced error. The principle that all legislative powers must be limited likely matters to the five conservative justices. Based upon oral argument, it may matter to some of the liberal justices as well. Justice Breyer, for example, noted his concerns about the scope of the power asserted and its potential for abuse in the future. Whatever the Court rules in this case, he noted, would apply to future Presidents and would empower future Congresses.

There are quite a few ways for the Court to approach the underlying question in Trump v. Mazars. Based upon oral argument, I suspect the question of limits - in particular, the question whether upholding the House subpoenas at issue here opens the door to an unlimited subpoena power - will feature in the Court's ultimate resolution of the case.