On a recent episode of Stanford Legal, co-hosts Professors Pam Karlan and Diego Zambrano sat down with Professor Michael W. McConnell, a constitutional law scholar and former federal judge, to discuss a major legal challenge to presidential tariff powers. In April, President Trump declared a national emergency and claimed authority to impose tariffs, throwing global trade into uncertainty and upending existing agreements. McConnell is among the attorneys representing challengers in Trump v. V.O.S., a U.S. Supreme Court case contesting the president’s move. The Court has agreed to hear the case on an expedited basis, setting the stage for a high-stakes separation-of-powers battle.

As McConnell wrote in a recent New York Times op-ed, “The tariff litigation is shaping up as the biggest separation-of-powers controversy since the steel seizure case in 1952…most of the commentary has focused on the practical ramifications for the president’s trade negotiations and the American economy. But the cases may be even more important for the future of a fundamental component of the Constitution’s architecture: the separation of powers, intended by the founders to prevent any of the government’s three branches from becoming all powerful.”

The podcast conversation explores whether a president can impose tariffs without explicit congressional approval, the historical and constitutional roots of “no taxation without representation,” and what a redefinition of executive economic power could mean for the future.

The following is an edited and shortened version of the full podcast transcript, which can be found here.

Listen to the Podcast

Pam Karlan: Let’s start with what the president did with regard to tariffs.

On April 2, the president issued an executive order declaring a national emergency under the National Emergencies Act, citing what he called “large and persistent trade deficits” as an “unusual and extraordinary threat” to American interests. Those are the key trigger words in the International Economic Emergency Powers Act (IEEPA).

IEEPA is a successor to the old Trading with the Enemy Act, which grew out of wartime principles. When a country goes to war, its citizens can’t trade with the enemy; the government can also seize property and take related actions. IEEPA carries over many of those powers. Historically, they’ve involved embargoes, blockades, asset freezes—never tariffs.

The most famous use of IEEPA came during the Iranian hostage crisis, when Presidents Carter and Reagan used it to help secure the hostages’ release and return frozen Iranian assets. That’s the kind of situation IEEPA was meant for: asset freezes and similar measures, not taxation.

The taxing power—explicitly including tariffs—belongs to Congress. Article I, Section 8 gives Congress the power to impose “taxes, imposts and duties,” and “imposts and duties” are just synonyms for tariffs. In the early Republic, tariffs generated over 90% of federal revenues; controlling tariffs meant controlling the purse. Only recently have presidents been given limited authority over tariffs, and only through specific statutes. IEEPA doesn’t mention tariffs, and no president has ever used it for that purpose.

Diego Zambrano: Before we get into the weeds of the tariff arguments in the case you’re litigating, I want to step back to the broader issue of emergency powers. You’ve mentioned the history and the framers, and it seems like there’s this enormous web of emergency powers today. Do you see that as a big deviation from the Constitution’s original design, or are emergency powers appropriate and you just disagree with this one?

The president has no emergency powers vested by the Constitution. But if Congress chooses to give him defined emergency powers, I don’t think there’s anything wrong with that. In fact, there are situations where someone has to be able to act quickly in an emergency—you can’t always bring Congress together and pass something right away.

I do think there’s a problem with the National Emergencies Act because it’s extremely broad and unlocks powers under roughly 180 different statutes. When it was originally passed, Congress included a legislative veto so that if the president declared an emergency and Congress disagreed, it could immediately shut it down.

About ten years later, the Supreme Court struck down legislative vetoes in general—not specifically in connection with the Emergencies Act, but across the board. And yet the Emergencies Act remains on the books. Congress felt free to write such a broad statute because it believed it would retain control. Now we’re left with an unusually broad law but without the check Congress originally built in.

“This is, I think, the most far-reaching presidential action ever justified on an emergency basis.”    — Professor Michael McConnell

Pam Karlan: There are two separate issues here. One is whether Congress can give these emergency powers to the president, and whether it did so here. The other is what actually counts as an “emergency,” since there isn’t a clear definition of that, is there?

There’s no definition at all in the Emergencies Act.

Pam Karlan: And we have a president who seems to think everything is a five-alarm fire.

Yes, that’s true. But we should acknowledge that previous presidents have also used the power to declare emergencies pretty freely, and many are on the books covering all kinds of issues. What’s unusual here is that very few of those declarations involve something as sweeping as a major domestic tax. This is, I think, the most far-reaching presidential action ever justified on an emergency basis.

Pam Karlan: Let’s turn now to the tariffs case itself, including a little bit about how Trump v. V.O.S. came about and the claim you’re making. 

There are actually three cases that have been consolidated in what’s now Learning Resouces v. Trump. I’m involved in one of them, which I think is the most significant—not just because I’m involved, but because it has real plaintiffs with clear stakes. Our clients are five small businesses that have paid these tariffs and are suing for a refund. They’ve also been hit with higher input costs, in some cases enough to threaten their survival, though fortunately they haven’t gone under yet.

The second case was brought by 12 states, all represented by Democratic attorneys general. The third was filed by another group of businesses, led by Learning Resources. Our case was filed in the Court of International Trade, which is the proper venue under the statute governing tariff disputes. The Learning Resources case, by contrast, was filed in federal district court, so there was a jurisdictional question about where the litigation belonged. The Supreme Court resolved that by consolidating the cases, ensuring the issues can be decided together no matter how the jurisdictional question is resolved.

The Court has also put the case on an unusually fast track, setting it for argument in the first week of the November sitting. But this isn’t one of those emergency “shadow docket” matters where the Court acts without a developed record. Here, there’s a full decision on the merits from the Court of International Trade, a considered appellate ruling, full briefing, and now oral argument. It’s a normal case—just moving quickly.

That’s a far better posture than the typical shadow docket case, where the Court is often forced to wrestle with difficult issues for the first time without a decision below. This case doesn’t have that problem.

Diego Zambrano: Let’s talk about the Federal Circuit’s reasoning. In broad terms, the court held that “regulate importation” doesn’t authorize these tariffs. The key statute here, IEEPA, doesn’t give the president that power. But this was a 7–4 decision, and the dissenters offered a strong argument that IEEPA does authorize the tariffs. What do you see as the main point of disagreement between the majority and the dissent, especially when it comes to the statutory text?

The core disagreement centers on a single phrase in IEEPA that gives the president, in the event of an “unusual and extraordinary threat” and a declared emergency, the authority to “regulate importation or exportation.”

The majority held that this language does not include the power to impose tariffs. Regulation, they said, is distinct from taxation, and Congress explicitly vested the taxing power in itself. Even if IEEPA could be read to grant some limited authority affecting imports, it cannot be interpreted as giving the president an open-ended power to tax however he wants.

A lot of the legal argument turns on the history of IEEPA in the 1970s—how and why Congress enacted it. That legislative history is where the real substance of this dispute lies.

Diego Zambrano: We should note that the text “regulate importation” doesn’t include the word “tariff,” “customs,” “duty” or “tax.”

The government argues, quite strenuously, that the term “regulate” doesn’t exclude taxation—and that in some contexts it can include it. You could imagine, for example, a statute saying the FDA may “regulate cigarettes by imposing taxes.” That wouldn’t be incoherent.

But our position is that without that kind of specific context or language, you don’t read the bare word “regulate” as conferring the very different and significant power to tax.

Congress has passed a series of statutes giving the president explicit powers to impose tariffs under specific circumstances. For example, where a type of import or export endangers national securityt–for example, this might involve the export of militarily significant technology. The president is able to block that under that statute. Another statute provides that when another trading partner is engaged in dumping or other unfair trade practices that the president can respond with a tariff, but through a rather elaborate process.

Pam Karlan: And those other statutes come with a lot of process—and also substantive limits—on how tariffs can be imposed, how high they can go, and how long they can last. If the president can act under IEEPA instead, isn’t he essentially claiming unlimited authority to set both the size and duration of the tariffs?

Yes. And the most relevant statute here was passed just before IEEPA—Section 122 of the Trade Act of 1974. It specifically addresses large and serious trade deficits. Under that law, the president can raise tariffs, but only by up to 15%, and only for 150 days. Many of President Trump’s tariffs exceed those limits—50% on Brazil, 30% on India, and China fluctuates almost daily. They’re also not temporary; they’re effectively indefinite. Our position is that when Congress enacts a statute granting the president tariff authority but carefully limits how it can be used, it makes no sense to interpret another statute that doesn’t even mention tariffs as giving him unlimited power to do whatever he wants.

Diego Zambrano: The government also makes this “greater includes the lesser” argument. They say that if the president has the power to prohibit imports under the statute, it wouldn’t make sense to say he can’t also tax them. In their view, if you can exercise the greater power to ban imports entirely, you can certainly use the lesser power to tax them. How do you respond to that?

I’m happy to address the “greater includes the lesser” argument, because there are both historical and logical problems with it. Historically, IEEPA traces back to the Trading with the Enemy Act, which codified principles of the old law of war. That law prohibited imports and exports during wartime—it allowed embargoes and blockades, but not taxation. It was never used to impose taxes. So the line between prohibition and taxation is embedded in the history of these powers.

Logically, taxing isn’t actually a “lesser” power. For one thing, taxation raises revenue. President Trump has openly touted how many hundreds of billions of dollars his tariffs would bring in. That’s a powerful temptation that doesn’t exist with embargoes, which generate no money. Politically and practically, those are entirely different dynamics.

There’s also a constitutional point. Prohibitions target foreign entities, but tariffs are taxes on Americans. My clients are the ones who pay the bill. Tariffs are not paid by foreign governments, despite what the president sometimes says. And Congress has always closely guarded the power to tax U.S. citizens. “No taxation without representation” was one of the rallying cries of the American Revolution.

So the idea that the power to prohibit automatically includes the power to tax just doesn’t hold up. 

Diego Zambrano: There’s a key historical argument here tied to the origins of IEEPA. Before IEEPA, the same language about the president’s power to “regulate importation” appeared in the Trading with the Enemy Act. In 1971, President Nixon relied on that statute to impose a 10% global tariff. The government points to that episode in two ways: first, they argue the language carried over unchanged into IEEPA, so it should be read the same way; and second, they say Nixon’s actions created precedent for presidential tariff authority under that language. That, in turn, relates to the major questions doctrine—the idea that courts shouldn’t lightly assume Congress gave the president sweeping power to impose major, unprecedented economic measures. So, can you walk us through what happened in the Nixon case and how it matters here?

This history is very important. The government argues that the phrase “regulate importation or exportation” in IEEPA is identical to language in the Trading with the Enemy Act, a World War I statute. That law had never been used to impose tariffs—until 1971, when, for the first and only time, President Nixon relied on it to do so during a genuine emergency.

At that point, the international monetary system—the gold standard—was collapsing. In response, Nixon imposed a 10% import surcharge. It respected existing congressional tariff rates, increased them by 10%, and lasted less than five months.

Congress didn’t object to the economic policy itself—it was widely viewed as one of Nixon’s smartest moves—but lawmakers were alarmed by the scope of the power he claimed. Hearings followed, and witness after witness—including members of the administration—warned that the president’s authority under the Trading with the Enemy Act needed to be curtailed.

Congress responded in three steps: First, Section 122 of the Trade Act of 1974. Congress passed a new, narrow statute explicitly giving the president tariff authority in cases of “large and serious” trade imbalances, but capping increases at 15% and limiting them to 150 days. If the Trading with the Enemy Act already provided that power, there would have been no need for this new statute.

Second, Congress repealed the Trading with the Enemy Act except in cases of declared war.

Third, Congress enacted IEEPA—but made no mention of tariffs in the statute or its legislative history. That’s because it had already addressed presidential tariff powers through the Trade Act.

Nixon’s surcharge was challenged in customs court (the predecessor to today’s Court of International Trade), which held he lacked authority under the Trading with the Enemy Act. By the time the appellate court reversed and upheld Nixon’s action, the surcharge had already expired. All that remained was whether those who had paid the surcharge could recover it.

It’s important to note that Nixon’s tariffs were limited, temporary, and carefully structured. He operated entirely within the legal framework Congress had already established—raising rates that had been lowered by prior presidential action, not by Congress. That’s a very different situation from what’s being asserted under IEEPA today. 

Diego Zambrano: I want to close by asking about the major questions doctrine. Over the last couple of decades, the Supreme Court has increasingly used this doctrine to limit the power of agencies—and, in some cases, the president—when it comes to issuing regulations with major economic or political consequences. The Court has made clear that it won’t interpret a statute to grant that kind of sweeping authority unless Congress speaks very clearly. The argument here is that IEEPA shouldn’t be read to give the president this power precisely because it would have such vast economic and political significance. How do you see that issue playing out before the Supreme Court?

Some observers think this could be the key issue in the case. The government argues that because Congress carried over language from the Trading with the Enemy Act when it enacted IEEPA, that might suggest Congress left the door open. But the problem is—it isn’t clear. Congress didn’t use any language referring to tariffs, and there’s nothing in the legislative history to support the idea that it intended to delegate that kind of power.

Under the major questions doctrine, if Congress wants to give the president sweeping authority over matters of major economic and political significance, it has to say so clearly. That clarity is missing here.

There’s also a political dimension. This doctrine has been used frequently in recent years—mostly against actions by Democratic administrations. The Court invoked it to strike down the eviction moratorium during COVID, the student loan forgiveness program, the vaccination mandate, and several climate regulations under the Clean Air Act. In each case, the Court found that the statutes cited did not clearly grant the claimed authority.

If the Court applies the doctrine consistently, you’d expect it to require clear congressional authorization here as well. It will raise some eyebrows if the Court treats a Trump administration action differently from how it treated similar exercises of power by President Biden.

Michael W. McConnell is the Richard and Frances Mallery Professor and Faculty Director of the Constitutional Law Center at Stanford Law School, and a Senior Fellow at the Hoover Institution. From 2002 to 2009, he served as a Circuit Judge on the United States Court of Appeals for the Tenth Circuit. He was nominated by President George W. Bush, a Republican, and confirmed by a Democratic Senate by unanimous consent. McConnell has previously held chaired professorships at the University of Chicago and the University of Utah, and visiting professorships at Harvard and NYU. He teaches courses on constitutional law, constitutional history, First Amendment, and interpretive theory. He has published widely in the fields of constitutional law and theory, especially church and state, equal protection, and separation of powers. His book, “The President Who Would Not Be King: Executive Power Under the Constitution,” was published by Princeton University Press in 2020, based on the Tanner Lectures in Human Values, which he delivered at Princeton in 2019. His latest book, co-authored with Nathan Chapman, “Agreeing to Disagree: How the Establishment Clause Protects Religious Diversity and Freedom of Conscience,” was published by Oxford University Press in mid-2023. McConnell has argued 16 cases in the United States Supreme Court.