A U.S. appeals court ruled Friday that many of President Donald Trump's tariffs are illegal, dealing a major blow to the president's trade policy. The decision could severely undermine the president's ability to maneuver in the escalating global trade war, the New York Times reported in an analysis.

The US Court of Appeals essentially upheld an initial court ruling made in May that Trump does not have unlimited authority to impose tariffs on almost all imports into the country.

However, the ruling does not take immediate effect. Its implementation is expected to be delayed until mid-October, meaning the tariffs remain in place, at least temporarily. The US government has the option of appealing to the Supreme Court in the meantime.

In any case, the core of Trump's trade strategy is being called into question, which, based on a 1970s law , imposes sweeping tariffs on dozens of US trading partners, the NYT emphasizes.

Trump has used this law – the International Emergency Economic Powers Act, or IEEPA – to boost U.S. coffers and pressure other countries to make deals favorable to the United States. However, the law was originally intended to impose sanctions and embargoes on other countries.

The Trump administration had argued in court earlier yesterday that any restriction of its powers would cause economic chaos.

Furthermore, a few hours before the decision, the president's top economic advisers had expressed strong concern about the fate of the trade agreements the United States had concluded.

Among the agreements they mentioned is the one with the European Union, which made concessions to avoid further tariffs on its goods.

Trump's first reactions

The US president has been insisting for months that tariffs will make America rich again, while he has referred to the Great Depression and the risk of a return to it if his powers in the trade sector are limited.

In a social media post after yesterday's decision, Trump was critical, suggesting that he was preparing to appeal to the Supreme Court.

He spoke of a wrong decision, as well as political and partisan motives. They know that the United States of America will win in the end, he stressed, warning of great disaster for the country if the tariffs are lifted.

The powers of the president

The appeals court's decision concerns a huge volume of tariffs and some of the highest that Trump has announced, targeting countries such as China, Canada and Mexico. It also includes so-called retaliatory tariffs.

To enforce his trade policy, the American president relied on IEEPA, an old economic emergency law, which, however, makes no mention of tariffs.

Trump invoked the authority given to him by law to combat a widening set of threats, which he has said arise from a range of problems, from trade deficits to fentanyl imports into the United States.

Without the law in question, the president does not have the authority to impose tariffs with the speed and manner he is attempting to do so today and would have to get approval from Congress.

For now, there is no guarantee that he will achieve his goals through the Supreme Court. Leading lawyers and academics from across the US political spectrum have argued that the president has abused his powers.

Already, businesses and individual states have taken legal action against Trump's claims that he has unlimited power in the trade sector, emphasizing that they are financially harmed by the tariffs.

In May, a commercial court annulled many of the president's decisions on the grounds that the law does not grant him unlimited power.

The Trump administration quickly appealed. The new 7-4 ruling, issued late Friday, ruled for the second time that the scope of the tariffs the president has imposed is illegal.

The role of Congress

No president before Trump had invoked the Economic Emergencies Act to impose tariffs. During his first term, his advisers had questioned his tariff policy and his ability to enforce it.

However, after returning to the White House, Trump and his advisers adopted the new interpretation of the law, concluding that an economic emergency could be declared, citing the wide range of concerns and the large US trade deficit.

They came to see the law as a tool that allowed them to move quickly, according to Ted Murphy, an international trade specialist at the law firm Sidley Austin.

The president can do a lot in the trade sector, he said, adding, however, that the decision reminds everyone that only the Constitution gives Congress the power to impose tariffs on a large scale.

Trump's weapons

Even if Trump loses in the Supreme Court, however, he will still retain significant power over the formulation and implementation of his trade policy.

Among the weapons in his quiver is a trade law provision known as Section 232, which allows the president to impose tariffs that are related to the country's national security.

Trump has used this tool to impose tariffs on imported cars, as well as steel, and to propose imposing additional tariffs on semiconductors, pharmaceuticals and other products.

Other trade laws allow the president to impose more sweeping tariffs, but for a limited period of time. Section 122 of the Trade Act of 1974, for example, allows a president to impose tariffs of up to 15% worldwide for up to 150 days, which could be used as a temporary measure.

Another provision of the same law, known as Section 301, gives the president the ability to impose tariffs in response to unfair trade practices, provided that the government has previously conducted consultations and a relevant investigation.

Jake Colvin, president of the National Foreign Trade Council in the US, said that the decision to remove tariffs should wake up Congress to reclaim its authority to regulate tariffs.

He described the court's decision as positive, but explained that it is not yet clear whether it will provide substantial relief to businesses affected by Trump's trade war.