A day after a federal court ruled against President Trump’s latest global tariffs, his administration returned to the drawing board on Friday, trying to preserve its powers to wage economic warfare in time for high-stakes trade talks with China.

The latest legal blow concerned the 10 percent tariff that Mr. Trump imposed in late February on nearly all U.S. imports. The president unveiled that policy as a sort of temporary fix, after the Supreme Court tossed out his initial duties, but a panel of judges once again found that the White House had run afoul of the law.

The result was a familiar set of headaches for Mr. Trump, who has tried repeatedly — and with mixed success — to stretch his authority to tax imports without the express permission of Congress. By Friday, one of the president’s top aides signaled that an appeal was imminent, echoing the president, who told reporters shortly after the ruling that he would simply “do it a different way.”

Technically, the Court of International Trade only declared the president’s across-the-board, 10 percent tariff to be illegal. Otherwise, it did not issue an order forcing the government to stop collecting it from all importers, at least for now. Still, the outcome marked both a political and legal setback for Mr. Trump, who had spent much of the week issuing trade threats against Europe and preparing for talks in China.

Tariffs are expected to be a major topic on the agenda when Mr. Trump travels to Beijing to meet next week with his counterpart, Xi Jinping. Trade experts said the court decision could undercut the president’s leverage. Eswar Prasad, a professor of economics at Cornell University, said the ruling “severely handicapped” the administration’s ability to employ tariffs against foreign nations, leaving Mr. Trump with a “much weaker bargaining hand” when it comes to China.

“Any threats by Trump to hit China with broader and higher tariffs if Xi doesn’t bend to his will on economic and geopolitical matters now seem like empty bluster rather than credible ultimatums,” he said.

One of the president’s top trade advisers, Jamieson Greer, appeared to brush aside some of those concerns on Friday. During an interview on Fox Business, he criticized the court for ruling against the White House, claiming that some of the judges on the panel were “apparently just hellbent on importing more from China.”

Mr. Greer, who defended the president’s use of trade powers, added that the administration is “confident on appeal we’ll be successful.”

At the heart of the matter is Mr. Trump’s decision to invoke a trade power that no president had ever used. Known as Section 122 of the Trade Act of 1974, it permits the president to impose tariffs up to 15 percent for 150 days, but only in response to strict conditions, including a “balance of payments” crisis.

The term itself reflects a bygone concern from the time the law was adopted, when the U.S. dollar was pegged to gold, creating unique economic risks. But the Trump administration sought to argue that the law still applied today, pointing in part to the country’s persistent trade deficit, a different measurement, which reflects the gap between U.S. imports and exports.

In the end, a majority of judges on the Court of International Trade found the argument unpersuasive and sided with small businesses and states that had sued. It marked the second time that some of those challengers had prevailed against Mr. Trump, after they convinced the Supreme Court to invalidate his earlier use of emergency powers to impose withering tariffs.

The new decision raised the odds that the administration could soon have to pay back the billions of dollars collected from its 10 percent tariff, on top of the $166 billion that the government already owes to U.S. importers from its last legal defeat. But the fight appeared far from over, and much remained uncertain by Friday — not just for American businesses, which paid the cost to import goods, but for the Trump administration itself.

“President Trump has lawfully used the tariff authorities granted to him by Congress to address our balance of payments crisis,” Kush Desai, a White House spokesman, said in a statement. “The Trump administration is reviewing legal options and maintains confidence in ultimately prevailing.”

For one thing, the court only appeared to bar the collection of the president’s 10 percent tariff for some of the plaintiffs that sued, many legal experts said. That raised the odds that droves of U.S. businesses could soon mobilize and “file a court case” of their own asking for similar relief, said Ted Murphy, a top trade lawyer at the law firm Sidley Austin. He added that he also expected the trade court to pause implementation of its order pending an appeal.

The timing is important to Mr. Trump, who had always envisioned his across-the-board tariff as a stopgap that would allow the government time to prepare a set of more lasting rates using another set of authorities, known as Section 301. But that process was widely expected to take months, since the law requires the government to conduct investigations into other countries’ trade practices before Mr. Trump can apply new duties.

Those inquiries targeting dozens of countries are well underway, and the president at times has suggested the final rates could be set at new highs. Some experts believe the tariffs imposed using Section 301 could be more legally durable, though the administration could still face lawsuits over his aggressive use of the law.

Michael Lowell, the chair of the global regulatory enforcement group at the law firm Reed Smith, said the White House probably would not have to worry about “a broad attack on that authority.” But, he said, the courts had recently drawn something of a line in the sand, suggesting they would be “very skeptical of the administration looking to the past and finding and repurposing” other powers to advance its trade agenda.

Unlike the president’s other trade gambits, he has successfully applied tariffs in the past using Section 301, including on China. That left some analysts to conclude that Mr. Trump, while blemished, would still retain some leverage ahead of his trip to Beijing next week.

“Unless they have amnesia, China should remember quite vividly how during Trump’s first term, the U.S. imposed multiple rounds of tariffs under Section 301 on China during negotiations,” said Sarah Schuman, a former U.S. trade official who is now managing director at Beacon Global Strategies.

The administration still had multiple options “to increase tariffs on China in pretty short order,” she added.

Mr. Trump’s trip to China had been scheduled for April, but was delayed because of the war in Iran. U.S. officials have said their goals for the visit include establishing a “board of trade,” which would oversee commerce between the countries in an effort to balance trade and reduce the U.S. trade deficit with China

On Friday, Mr. Greer sketched out a long list of concerns that the administration planned to raise with its Chinese counterparts, from its adherence to past purchase agreements to its approach to artificial intelligence.

“There’s not really a situation where we go, we get China to change the way they govern, the way they manage their economy; that’s all baked into their system,” he said. “But I think there is a world where we find out where we can optimize trade between China and the U.S. to achieve more balance.”

Across Europe, the lesson from an old proverb just might be taking hold: Fool me once, shame on you; fool me twice, shame on me.

For the second time in under five years, Europe is contending with an energy crisis set off by a war. Europeans have responded to the price shock by rushing to line up heat pumps, solar panels and electric vehicles. They are hoping to lower their bills and reduce their reliance on imported fossil fuels.

In March, the first month of the war in the Middle East, more than 344,000 electric vehicles were registered across Europe, over 40 percent more than a year earlier, according to the European Automobile Manufacturers’ Association. Solar panel sales for Britain’s biggest power company, Octopus Energy, jumped 50 percent. And in Germany, inquiries about residential solar systems doubled compared with recent months, according to E.ON, an energy company.

Over the first three months of the year, about 575,000 heat pumps were sold in 11 large European countries, up 17 percent from a year earlier, the European Heat Pump Association said. The increases were particularly large in France, Germany and Poland.

For Heizma, an Austrian company that installs heat pumps, solar panels and other residential electrification services, sales in March and April broke records.

Since the war stopped a vast majority of fuel shipments through the Strait of Hormuz, the price of European natural gas, which is relied on to heat homes and power factories, has risen about 40 percent.

As prices spiked, interest in alternative energy supplies kept rising. Michael Kowatschew, a founder of Heizma, said customer inquiries were up 20 percent. Many of them invoked the importance of “resilience” and “European sovereignty.”

Russia’s invasion of Ukraine in 2022 was a jolt for Europe, which had been dependent on Russia for critical supplies of energy. European governments turned to other gas and oil exporters, including the United States.

Europeans are noticing “more and more how dependent we are not only on fossil fuels but, through fossil fuels, on other countries and other regions,” Mr. Kowatschew said.

The European Union has spent an additional 24 billion euros on energy imports in under two months, said Ursula von der Leyen, the president of the European Commission.

“Households are now seeing that they are only one Trump-ignited war away from very expensive tank refueling or heating bills,” said Elisabetta Cornago, an energy and climate policy expert at the Center for European Reform.

This “shock-awareness factor” means that demand for electric vehicles, heat pumps and solar panels is likely to keep rising, she said.

Demand has increased even as European governments have started to cut taxes on energy bills and diesel and gasoline at the pump to shield households. The costs of solar panels and electric vehicles, still out of reach for some households, are becoming more affordable. Last week, Volkswagen, Europe’s largest automaker, revealed a new electric vehicle model with a starting price under €25,000 (about $29,000), more than 25 percent below a comparable VW popular model.

In Britain, the government said it would allow the sale of plug-in solar panels within the next few months. These devices, which can be attached to a balcony, can help curb energy bills and don’t require the more expensive installation of rooftop panels. They will be widely available in supermarkets and online.

In the meantime, rooftop solar has become more popular. Danny Hirst, the managing director at the Green Way Solar, which installs solar panels in England, has noticed a sharp increase in interest. Last fall, his company was receiving about 10 inquiries a week. Now, it sometimes gets 20 in a single day, he said.

“The general feeling that we’re hearing from clients now is that they’re just getting fed up with the uncertainty of energy prices,” Mr. Hirst said.

But will the interest be sustained? Companies and business groups said it was too soon to know.

For customers, there’s red tape. It can take weeks or months, partly because of regulatory approvals, for a customer to go from deciding to buy a heat pump or solar panels to installing them.

Then there is the push-pull issue of government policies over financial incentives or subsidies, which can drive consumer demand but cause it to taper if they are not designed properly.

Since the war started, countries across Europe have already put in place short-term measures to lower energy costs — more than €10 billion worth, according to an estimate by Bruegel, a think tank in Brussels.

The measures, such as tax cuts on gas at the pump and electricity bills, are predominately aimed at large parts of the population. Experts said governments should target their assistance to the most vulnerable households, while spending more to subsidize low-carbon energy.

This has echoes of the crisis from 2022. At the time, Europe had suddenly shifted away from Russian gas imported via pipelines, a prominent source of fuel. Energy prices rose sharply. Demand for electric vehicles, solar panels and heat pumps jumped.

But when Europe found other sources of natural gas and prices dropped from their peak, interest in renewable technologies waned. Meanwhile, governments had spent hundreds of billions of dollars to shield households and businesses from high energy costs, further reducing the urgency for households to switch to renewables, some analysts said.

Simone Tagliapietra, an energy and climate policy expert at Bruegel, said the lesson for policymakers from 2022 was that they should increase their support for low-carbon technologies, not broad based-measures that cheapen energy from oil and gas. The moment, he said, presents an opportunity for governments.

“We are facing a full-fledged oil and gas crisis,” Mr. Tagliapietra said.

At the same time, history shows that financial incentives needed to sustain consumer interest in technologies like solar panels must be consistent.

Mr. Hirst of the Green Way Solar has been in the solar industry for nearly a dozen years and has experienced the market’s ups and downs. There was a boom right after the 2022 crisis, he said, but then sales dropped. The promise of subsidies drove up interest in renewable technologies, but consumers then waited to make sure they received a subsidy before deciding to install solar panels or heat pumps.

There is a risk that this could happen again.

In Austria, demand for heat pumps dropped in the first three months of this year when some government funds for subsidies ran out.

Mr. Kowatschew at Heizma, the Austrian installation firm, said he was cautious about expanding too quickly. The company was established only two years ago. Its focus is on finding ways to make the installation process faster and more efficient so that workers can outfit two heat pumps a week instead of one, he said.

Still, business is good. Heizma made about €2 million in revenue in April, he said.

“Everyone now knows electrification makes sense,” he said. “It makes a lot of sense to switch to heat pumps, to solar and green electricity.”