President Donald Trump ushered in the implementation of his so-called reciprocal tariffs early Thursday at midnight, proclaiming that “billions of dollars in tariffs are now flowing into the United States” as a federal court continues to litigate Trump’s authority to impose them.

“Billions of dollars, largely from countries that have taken advantage of the United States for many years, laughing all the way, will start flowing into the USA,” Trump wrote on his social media platform Truth Social. “The only thing that can stop America’s greatness would be a radical left court that wants to see our country fail!”

The question of whether a president has the authority to impose sweeping tariffs is currently being tested in the U.S. Court of Appeals for the Federal Circuit.

While Congress historically holds the authority to regulate commerce with foreign nations, Trump has defended his authority to impose tariffs citing the International Emergency Economic Powers Act, which expands the president’s authority as it relates to sanctions and trade under circumstances where there exists an “unusual and extraordinary threat.” That threat, Trump has said, has been the United States’ trade imbalances.

Whether Trump’s position is validated by the federal court remains to be seen, though some experts argue Trump’s argument is a losing one.

Markets largely

remained stable

, however, as the wave of tariffs went into effect, whereas the value of the U.S. dollar dipped slightly.