The Volokh Conspiracy
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In today's Supreme Court oral argument in Trump v. Mazars, one of two cases concerning the scope of Congress' power to subpoena President Trump's financial documents, House of Representatives lawyer Douglas Letter repeatedly failed to identify any limiting principle constraining Congress' powers to subpoena the president's records. Cornell Law Professor Michael Dorf and co-blogger Jonathan Adler argue that this was a serious error, making it likely that the five conservative justices will rule against the House. They compare it to Clinton Administration Solicitor General Drew Days' famous mistake in United States v. Lopez (1995), where he was unable to articulate any limits to Congress' power to regulate interstate commerce. The result was the federal government's first defeat in a Supreme Court Commerce Clause case in many decades.
Josh Blackman argues that Letter did not make a mistake, but rather deliberately refused to concede any limits to his client's power.
Either way, Letter's failure to identify a limit is a weakness in the House's case, and one that could well lead to defeat. Fortunately, however, finding a limit is actually easy. Whether Letter's faux pas was an unforced error or a deliberate tactic, the Court is not bound by it. It can readily rule in favor of the House without giving Congress unlimited subpoena power.
Ironically, Drew Days' defeat in 1995 is a big part of the reason why Douglas Letter's case need not suffer the same fate. From the New Deal era to the 1990s, many legal commentators assumed there were no longer any judicially enforceable structural limits to Congressional legislative power. But beginning in the 1990s, the Rehnquist and Roberts courts decided a series of cases that reinvigorated such limits. Among other things, the Court ruled that the Commerce Clause cannot be used to regulate some types of "noneconomic activity" or impose mandates on "inactivity," that the federal government may not commandeer state governments, and that there are limits to its powers under the enforcement clauses of the Fourteenth and Fifteenth Amendments. Most recently, in Murphy v. NCAA, the Court ruled that Congress cannot pressure states to ban sports gambling under their own laws, a decision that had important implications for other assertions of federal power, including attempts to coerce sanctuary cities.
Both sides in Mazars agree that Congress can only use its subpoena power in these cases if there is a "valid legislative purpose." Obviously, there cannot be such a purpose in cases where Congress seeks to enact legislation that is beyond the scope of its powers. And under the federalism decisions of the last thirty years, those powers now have real, even if still modest, limits.
For example, Congress could not subpoena information related to Trump's many affairs and his divorce settlements with his two previous wives. Marriage and divorce are matters largely left to state regulation, not federal. Similarly, Congress could not use its legislative authority to investigate whether it should force state or local governments to curtail possibly unethical business dealings by the Trump family. The anti-commandeering rule forbids such laws.
Despite the Court's recent federalism decisions, congressional legislative power remains very broad. Some subjects that Congress cannot regulate directly might nonetheless be subject to investigation, because they are relevant to matters over which Congress does have authority. But if there is a problem here, it is not the lack of a limiting principle on Congress' subpoena power, but insufficient judicial enforcement of substantive limits on the scope of congressional authority.
I have long argued that the Court should enforce such limits more aggressively. But, until then, it stands to reason that any matter on which Congress may legislate is also one that it can investigate in order to get relevant information. In the case of Trump's financial records, Congress surely has the power to legislate on conflicts of interest in the executive branch, of which Trump's business activities create many. His records are also relevant to Congress' power to legislate income tax laws, as there may be good reason to impose special restrictions on the president and other high-ranking federal officials.
Congress' motives in conducting such investigations may not be purely public-spirited. The president's partisan opponents could potentially use the information they uncover for political purposes. But political self-interest is at the heart of a great deal of legislative activity, and does not thereby render that activity unconstitutional. There is a crucial distinction here between Congress' possible political motives here, and Trump's anti-Muslim motives in the travel ban case. Discrimination on the basis of religion is unconstitutional (even if cloaked under supposedly neutral criteria), whereas seeking political advantage is not.
Steve Sachs points out that Congress could potentially use subpoena power to investigate issues beyond the scope of its legislative authority because it has the power to initiate constitutional amendments. A proposed constitutional amendment can legitimately deal with issues that Congress cannot legislate about under the existing Constitution. However, if the amendment power is the only basis for a subpoena, Congress would at the very least have to be in the process of actually holding hearings or otherwise considering some potential amendment. And if the supposed amendment turns out to be a complete sham cooked up purely for purposes of subpoenaing information, that fact is likely to leak out, and courts should be able to take notice of it and rule accordingly.
Douglas Letter's inability or unwillingness to identify a limiting principle was indeed an error in some ways analogous to Drew Days' failure in Lopez. But Days' defeat could yet turn out to be Letter's salvation.
UPDATE: Josh Blackman responds to this post with some thoughtful commentary here. He argues that Congress can always get around the limits set out above by using either the amendment power or the spending power. On the amendment power, he claims that almost any information can be subpoenaed for purposes of considering a constitutional amendment, even if that amendment has no chance of passing. Such an amendment need not be a "sham" because some people might sincerely support it. However, what distinguishes a "sham" amendment from a genuine one is not the likelihood of passing, but whether consideration of the amendment is purely a pretext for seeking out information otherwise unavailable to Congress. The sham nature of the amendment would be hard to conceal from the courts, given the large number of people who would need to be involved in any attempt to consider an amendment in Congress.
On the spending power, Josh is right that, under current precedent, Congress can use the spending power to incentivize states to take actions that Congress could not mandate directly. However, as the Trump administration has found out in a series of sanctuary city cases, the spending power, too, has substantive limits, including that it cannot be used to coerce states, that conditions imposed on them must related to the purpose of the grant in question, and so on.
Even if it is the case that almost any information might be relevant to some type of legislation, Congress is allowed to enact under current Supreme Court precedent, there are nonetheless limits to the purposes for which Congress can seek out the information. By analogy, we would not say that law enforcement agencies' power to acquire information is unlimited merely because almost any type of information might potentially be relevant to some kind of investigation they are empowered to conduct. They still have to show that the information sought in any particular case will be used for a permissible purpose. The same applies to Congress' subpoena power.
If Congress' power to subpoena information is still too broad, the fault lies not in the scope of the subpoena power, but in the scope of the substantive legislative power the former is supposed to facilitate. It is the latter, not the former, that has too few limits. After all, it makes little sense to suggest that Congress has the power to legislate on X, but not the power to acquire relevant information about it. Those who think there are too few constraints on Congress' subpoena power should focus their efforts on constraining its power to regulate and spend, which remain far beyond what is permitted by the text and original meaning of the Constitution. That is true of the spending power, as well as many of its other authorities.