A federal appeals court said the president overstepped his authority when he imposed sweeping import duties

Donald Trump suffered the biggest defeat yet to his tariff policies on Friday, as a federal appeals court ruled he had overstepped his presidential powers when he enacted punitive financial measures against almost every country in the world.

In a 7-4 ruling, the Washington DC court said that while US law “bestows significant authority on the president to undertake a number of actions in response to a declared national emergency”, none of those actions allow for the imposition of tariffs or taxes.

It means the ultimate ruling on the legality of Trump’s tariffs, which were famously based on spurious economic science and rocked the global economy when he announced them in April, will probably be made by the US supreme court.

Here’s what to know.