Tariff case goes to Supreme Court - If this decision is allowed to stand, it will literally destroy the United States of America, Trump said angrily

The US Court of Appeals has ruled illegal the tariffs imposed by Donald Trump on almost all the countries with which he trades.

The ruling confirms a May ruling by the Court of International Trade, which also rejected Trump's argument that his tariffs were authorized under an emergency economic powers law.

The court did not stop the tariffs from being implemented, but said they would remain in effect until mid-October, paving the way for the U.S. Supreme Court.

The BBC attempts to explain how the court ruling could affect the US president's main policy.

In a 7-4 decision, the Court of Appeals upheld a lower court's ruling that Trump lacked the authority to impose global tariffs.

This is mainly due to the law that Trump used to justify his policy, the International Emergency Economic Powers Act (IEEPA), which, according to the judges, does not grant him the authority to impose tariffs, taxes or similar measures.

The US Court of Appeals rejected Trump's argument that the tariffs were legal under his emergency economic powers, calling them invalid as contrary to law.

Trump immediately criticized the decision, writing on Truth Social a few hours later that the appeals court is highly biased and the decision is a disaster for the country. If allowed to stand, this decision will literally destroy the United States of America, he said.

• What is IEEPA?

This old law, which Trump has used repeatedly in both of his terms, gives the US president significant authority to respond to a national emergency or a serious foreign threat.

The 1977 law states that the president can use various economic measures to address any unusual and extraordinary threat, originating in whole or in large part outside the United States, to the national security, foreign policy, or economy.

The law has also been used by Presidents Barack Obama and Joe Biden, who invoked it to impose sanctions on Russia after its illegal annexation of Crimea in 2014 and again after its full-scale invasion of Ukraine eight years later.

But the appeals court said in its ruling that the emergency law does not give the president broad authority to impose tariffs.

IEEPA neither mentions tariffs (or their synonyms) nor includes procedural measures that place clear limits on the president's authority to impose tariffs, the judges said.

Trump had argued when he announced his global tariffs that the trade imbalance harmed US national security and therefore constituted a national emergency, but the court ruled that imposing tariffs was not within the president's authority.

• Why is the court decision important?

Beyond the fact that it is a serious blow to one of the main pillars of Trump's policy, the federal appeals court's decision may have a direct impact on the American economy, with consequences that will also be felt in global markets.

Tariffs are taxes that businesses must pay for importing certain products from abroad and can affect sales and profit margins.

Businesses will face uncertainty, Dr. Linda Yu, an economist at the University of Oxford and the London Business School, told BBC Radio 4's Today programme.

Tariffs are intended to prevent domestic companies from purchasing foreign products, thereby affecting international trade.

As countries wait to see whether the US Supreme Court will consider the case - which seems likely - they may decide to postpone their business dealings with the US.

• What's next?

The case will likely go to the U.S. Supreme Court, a challenge that Trump hinted at on Truth Social.

"Tariffs were allowed to be used against us by our careless and foolish politicians. Now, with the help of the U.S. Supreme Court, we will use them to benefit our Nation and make America rich, strong and powerful again!" he said.

The conservative majority on the Supreme Court is more likely to agree with the president's view.

Six of the nine judges have been appointed by Republican presidents, including three chosen by Trump during his first term in the White House.

However, the court has shown a critical attitude towards presidents when they appear to be exceeding their powers in policies that are not directly authorized by Congress.

During Joe Biden's presidency, for example, the court expanded on the so-called important questions doctrine to invalidate efforts by Democrats to use existing laws to limit greenhouse gas emissions from factories and to write off student loans for millions of Americans.

• What will happen if the tariffs are ultimately found to be illegal?

A federal appeals court ruled 7-4 that Trump's nearly blanket tariffs are illegal. It has now given the U.S. government until mid-October to appeal to the Supreme Court in a case that has implications for both the U.S. economy and trade relations with the rest of the world.

If the Supreme Court upholds the decision, it could cause uncertainty in financial markets.

Questions will arise about whether the US should return billions of dollars collected from import taxes on products.

It could also be questioned whether major economies - such as the UK, Japan and South Korea - are bound by the individual trade deals they secured with the US before the August deadline. Other deals under negotiation could also be in turmoil.

If the appeals court's decision stands, it would also be a huge blow to Trump's political power and reputation as a negotiator. But if it is overturned by the Supreme Court, it would have the opposite effect.

• Are there still tariffs in effect?

This decision concerns Trump's reciprocal tariffs, which include a patchwork of different rates in most countries around the world, including taxes on products from China, Mexico and Canada.

These tariffs on nearly all products from nearly every country the U.S. trades with will remain in effect until mid-October. After October 14, they will no longer be enforceable, the appeals court said.

Separately, tariffs on steel, aluminum and copper, imposed under different presidential powers, will remain in place and are not affected by the court's ruling.