Twenty five US states sued the administration of US President Donald Trump on Monday over new tariffs of 10% to 12.5% on goods from 60 trading partners.
The tariffs came into effect in July, targeting countries including the UK and China as well as the European Union, over Washington's contention that they have failed to properly tackle forced labour.
In a legal document seen by the BBC, the coalition of Democratic states said the decision was "arbitrary, capricious, and contrary to law."
In response, White House spokesman Kush Desai said: "The US is using its lawful authority" to address practices that burden American businesses.
Desai added that any foreign country's failing to deal with the importation of goods produced with forced labour was "unreasonable" and must be addressed.
The new tariffs were imposed on major trading partners like Japan, Brazil and Taiwan under Section 301 of the 1974 US Trade Act, legislation which is designed to target nations that use forced labour.
The duties cover 99.4% of US imports, according to the Office of the US Trade Representative (USTR).
The lawsuit said the Trump administration "cannot use forced labour as a pretext to continue its illegal tariff scheme."
"The tariffs the USTR imposed are so broad that they defy the USTR's own stated aims and make a mockery of the statute used to justify them," it said.
