The blockbuster federal court ruling that halts President Donald Trump from imposing some of his most swee

The US Court of International Trade on Wednesday blocked Trump from relying on a 1977 law dealing with economic emergencies to impose sweeping duties on much of the world.

It did so in part by noting separation-of-powers theories the Supreme Court has used to shut down some of Biden’s policies, such as his efforts to forgive student loans, curb power plant emissions and extend a moratorium on evictions at the tail end of the pandemic.

“There’s a broader movement in this direction,” said Andrew Morris, senior litigation counsel at the New Civil Liberties Alliance, a libertarian-leaning law group that is active at the Supreme Court and that sued Trump over the tariffs in a separate case.

ping tariffs rests in part on a legal theory that conservative groups repeatedly used at the Supreme Court to block former President Joe Biden’s agenda.

A push by the majority-conservative Supreme Court to use what’s known as the “major questions doctrine” to trim the power of the White House and federal agencies to act without congressional approval may play a role when the case inevitably works its way up to the high court.

Trump initially pledged to bring an emergency appeal to the Supreme Court within days, but a federal appeals court on Thursday afternoon blocked the lower court’s order pending further legal action – meaning Trump’s tariffs will remain in place for now while the litigation continues.

“The general trend is that the court is looking closely at whether Congress has delegated certain power to the executive branch – agencies and presidents,” Morris said. “That trend weighs against the president in this case.”

In 2023, the Supreme Court relied on what’s known as the major questions doctrine to block Biden’s student loan forgiveness plan. That doctrine requires Congress to “speak clearly” when it intends to authorize a president to take actions of “economic or political significance.” In other words, if Congress doesn’t explicitly include language in a law giving the president power to act in some way, that action may be legally suspect.

The Supreme Court in 2022 curbed the Environmental Protection Agency’s ability to regulate carbon emissions from power plants, a major defeat for Biden that also relied heavily on the major questions doctrine.

In both cases, the policies were challenged by Republican attorneys general in conservative states.

The trade court’s opinion also flicked at what’s known as the “nondelegation doctrine,” or the idea that Congress can’t delegate its power to federal agencies. The Supreme Court is currently considering a case it will likely decide in June that touches on that same doctrine.

That appeal involves the multibillion-dollar Universal Service Fund, which Congress created in 1996 to offset the cost of phone and internet service for low-income Americans. A conservative “consumer awareness group” is challenging that fund, arguing it amounts to a tax levied by the Federal Communications Commission. It is Congress that holds the power to tax, not the executive branch.

The federal trade court nodded to both theories in its opinion Wednesday as “tools” that could be used to resolve the case.

“These tools indicate that an unlimited delegation of tariff authority would constitute an improper abdication of legislative power to another branch of government,” the court wrote. “Regardless of whether the court views the president’s actions through the nondelegation doctrine, through the major questions doctrine, or simply with separation of powers in mind, any interpretation” of the law “that delegates unlimited tariff authority is unconstitutional.”

The administration said the ruling “threatens to unwind months of foreign-policy decision-making and sensitive diplomatic negotiations, at the expense of the nation’s economic well-being and national security.”

During Trump’s first administration, the Supreme Court declined to hear appeals over Trump’s 25% tariffs on foreign steel. But those tariffs were levied under a different legal authority.