Canada has fought COOL and twice won trade-dispute victories, forcing the U.S. to abandon compulsory COOL.
But U.S. President Donald Trump has said he favours restoring COOL for the meat industry.
The lawsuit was brought by the Ranchers-Cattlemen Action Legal Fund, United Stockgrowers of America, the nation's largest group of independent cattle producers, and the Cattle Producers of Washington.
"Consumers understandably want to know where their food comes from," said David Muraskin of Washington, D.C., an attorney for Public Justice, which filed the lawsuit.
"With this suit, we're fighting policies that put multinational corporations ahead of domestic producers and shroud the origins of our food supply in secrecy."
The lawsuit says the change to drop mandatory COOL violated the nation's Meat Inspection Act, which required that slaughtered meat from other countries be clearly marked.