Workers remove a coil from the production line for quality-control testing during steel production at the NLMK Indiana steel mill on March 15, 2018 in Portage, Indiana.  (Photo by Scott Olson/Getty Images)
Washington CNN  — 

The US Supreme Court declined Monday to hear a challenge to President Donald Trump’s 25% tariffs on foreign steel.

The case was brought by the American Institute for International Steel, which argued that the legal tool used by the President to impose the tariffs, known as Section 232, is unconstitutional.

It’s the second time the court refused to hear the case.

Congress has jurisdiction over trade, but it has delegated some of its power to the executive branch. Section 232 allows the President to impose tariffs in order to protect national security.

The trade group argued that Section 232 itself is unconstitutional because it puts no limits on the President’s discretion to put tariffs on imports.

Trump imposed the tariffs on foreign steel in March of 2018. They were meant to protect domestic steal producers by making their competitors’ products more expensive. But the duties ended up hurting US companies that import steel, like nail and farm equipment manufacturers, costing them money.

Trump has also threatened to use Section 232 to impose tariffs on foreign-made automobiles. He used a different power, known as Section 301, to impose tariffs on billions of dollars of Chinese-made goods. That legal power allows the executive branch to impose tariffs if it finds there are unfair trade barriers to US exports.