AMNA NAWAZ: The Trump administration's sweeping tariff plan may be on shaky ground after a Supreme Court hearing focused on his authority to impose the measures.

Several justices on the court questioned the legality of the tariffs and how much power the president has to broadly enact his agenda.

Here's Justice Neil Gorsuch with U.S.

Solicitor General John Sauer.

NEIL GORSUCH, U.S.

Supreme Court Associate Justice: What would prohibit Congress from just abdicating all responsibility to regulate foreign commerce, for that matter, declare war to the president?

D. JOHN SAUER, U.S.

Solicitor General: We don't contend that he could do that.

If it did... NEIL GORSUCH: Why not?

D. JOHN SAUER: Well, because we're dealing with a statute, again, that has a whole set of... NEIL GORSUCH: I'm not asking about the statute.

General, I'm not asking about the statute.

I'm asking for your theory of the Constitution.

AMNA NAWAZ: Meanwhile, attorney Neal Katyal, arguing four small businesses challenging the tariffs, said the case was about more than the president's agenda.

NEAL KATYAL, Attorney for Tariff Opponents: This case is not about the president.

It's about the presidency.

It's not about partisanship.

It's about principle.

And, above all, it's about upholding the majestic separation of powers laced into our Constitution that is the foundation for our government.

AMNA NAWAZ: The case will have major implications for the global economy and the limits of future president's power.

For more on this, I'm joined by the "News Hour"'s Supreme Court analyst.

That is Amy Howe of SCOTUSblog.

Good to see you.

AMY HOWE: Good to see you too.

AMNA NAWAZ: So, before we jump into what happened today, what exactly is the question before the Supreme Court on this case?

AMY HOWE: So the question at the center of the case is the president's power to enact these sweeping tariffs.

And the president relies on a 1977 law called the International Emergency Economic Powers Act, the somewhat unwieldy acronym IEEPA.

And the challengers say that that law simply does not give him the authority that he's claiming.

AMNA NAWAZ: You heard in that exchange there Justice Gorsuch injecting a little skepticism in that line of questioning.

Did we hear that from other conservatives on the court as well?

AMY HOWE: We did.

We heard from -- Chief Justice John Roberts, for example, told Solicitor General John Sauer that perhaps the major questions doctrine, which is the idea that if Congress wants to give the power to make decisions of vast economic and political significance, it needs to say so clearly, and he suggested that the president's tariffs might run afoul of that doctrine.

And it's interesting because this was a doctrine on which the Supreme Court relied to strike down several Biden era policies, like the student loan debt relief program, the COVID era restriction on evictions, one of the vaccine mandates for COVID-19.

And so it will be interesting to see whether or not the conservative justices also apply this to the tariffs.

AMNA NAWAZ: We also did hear some sympathy toward the argument from the president's lawyers here that the president does have broad authority when it comes to things like foreign affairs.

That includes trade in some cases.

Does any of this give us any indication of how this case will go?

AMY HOWE: You know, we did hear from Justice Samuel Alito, Justice Clarence Thomas, and Justice Brett Kavanaugh.

Justice Samuel Alito, for example, said that this was intended to be a statute in which Congress gave the president broad powers to deal with emergencies.

And so he seemed sympathetic.

And so I think it will be a close vote.

And, certainly, when the U.S.

Court of Appeals for the federal circuit heard this case, the lower court, it divided 7-4.

It did not necessarily divide on ideological lines.

The dissent in that case was written by a judge who was an Obama appointee.

So it certainly seemed like Justice Gorsuch was skeptical of Trump's tariffs.

And this one too might not divide on ideological lines.

AMNA NAWAZ: There's clearly a lot at stake.

We know the treasury secretary, Scott Bessent, the commerce secretary, Howard Lutnick, were both at the hearing today.

We saw President Trump himself last night post online that this was a life-or-death case in terms of the country.

If they lose, what's at stake?

What could that look like, not just with regard specifically to tariffs, but for the broader agenda here?

AMY HOWE: Yes, so, as you say, there are a couple of -- we're operating at a couple of different levels.

Justice Amy Coney Barrett asked, like, what happens if we rule for you talking to Neal Katyal?

And she suggested that it would be a mess if the government had to give refunds of these billions of dollars' worth of tariffs.

And Neal Katyal gave the justices a smorgasbord of options that they could go with if they decided that the tariffs were illegal, rather than just sort of order the government to give everyone their money back.

But then there's the question of the tariffs, that, certainly, one of the challengers arguments for why Congress in this statute, IEEPA, didn't give the president the power to impose tariffs is that there are other laws that allow the president to impose tariffs, but with some restrictions.

And so the Trump administration could try to impose the tariffs relying on other laws.

They could go to Congress.

And then, with the broader question, this is the first test of several tests that we're going to see at the Supreme Court this term involving the president's powers.

AMNA NAWAZ: Any indication how quickly they will move on this case?

AMY HOWE: It's a really good question.

And, certainly, we know that they can move quickly.

In January, they issued a decision in a week in the TikTok case.

I certainly don't think that they're going to move that quickly in this one, but the Trump administration did ask the justices to move quickly in this case.

This case was highly expedited.

So I don't think this is going to be one of those cases where we're going to be here at the end of June talking about it.

I think it's more likely to be sometime this winter or early spring at the latest.

AMNA NAWAZ: All right, that is "News Hour" Supreme Court analyst Amy Howe of SCOTUSblog.

Amy, thank you so much.

AMY HOWE: Thanks for having me.