Key justices on the conservative majority of the US Supreme Court have appeared skeptical of President Donald Trump's claim that he has the authority to impose tariffs on imported goods.
This potentially jeopardizes one of the key points of his political program and represents the biggest legal test so far of his second presidential term, during which he is taking unprecedented actions.
The Republican Trump administration is trying to defend tariffs, a central part of Trump's economic policy, before the Supreme Court. Lower courts have already ruled that the Emergency Powers Act, which Trump is invoking, does not give him the near-unlimited right to impose and change tariffs on imported goods.
The US Constitution says that Congress has the right to establish tariffs, but the Trump administration claims that in emergency situations the president has the right to regulate imports himself - and that includes tariffs.
In her arguments, Judge Amy Coney Barrett, who is considered a conservative, asked the federal government representatives an uncomfortable question: "Has there ever been another case in which a legal act used such language to grant such authority?"
Justice Neil Gorsuch, also a conservative, asked government representatives whether Trump's position meant that too much power from Congress was being transferred to the president.
"Is the constitutionally-based delegation of taxing powers to Congress - the power to pick pockets of the American people - any different (than this tariff)?" Gorsach asked, adding: "Has it ever been any different since this country was founded?"
Trump believes that the case that has reached the Supreme Court is the most important in US history and claims that a ruling against him would be catastrophic for the economy.
Those who dispute his legal argument say that the 1977 law governing emergency powers, which Trump is invoking, does not even mention tariffs, and that no other president before him has used the law to impose them.
A group of small entrepreneurs says that customs duties are pushing their businesses towards bankruptcy.
The case before the Supreme Court concerns two tariff packages. One, from February, targets products from Canada, China and Mexico. It was introduced by Trump after he declared a national emergency over drug trafficking. The second package contains "reciprocal tariffs" that Trump announced in April for the vast majority of countries around the world.
A slew of lawsuits against the Trump administration followed, both from states with opposition Democratic administrations and from small businesses, due to the imposition of tariffs on everything from plumbing equipment to feminine hygiene products.
Lower courts have struck down many of Trump's tariff orders for illegal use of emergency powers. The U.S. Supreme Court, however, could see things differently.
It was Trump, in his first presidential term (2017-2021), who contributed to the creation of the current conservative majority on the Supreme Court after some justices died and some retired.
The new Supreme Court, with six conservatives and three liberals, has given Trump a series of important victories in situations where the court is required to act urgently. But few of Trump's broad-based conservative policies have been tested before the highest court in the United States.
The Supreme Court was skeptical of the way former President Joseph Biden, a Democrat, used his executive powers, and struck down some of his orders, such as the one on student loan forgiveness totaling $400 billion.
Trump's critics say Trump should be treated the same - especially since his policies have a much greater economic impact than Biden's.
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