The United States today filed a civil complaint against the state of California, several of its officers, the California Air Resources Board, and the Western Climate Initiative Inc., for unlawfully entering a cap and trade agreement with the Canadian Province of Quebec.

“The state of California has veered outside of its proper constitutional lane to enter into an international emissions agreement. The power to enter into such agreements is reserved to the federal government, which must be able to speak with one voice in the area of U.S. foreign policy,” said Assistant Attorney General Jeffrey Bossert Clark of the Justice Department’s Environment and Natural Resources Division. “California’s unlawful cap-and-trade agreement with Quebec undermines the President’s ability to negotiate competitive agreements with other nations, as the President sees fit.”

The Supreme Court has recognized that the interests of cities, counties and states, and the American people as a whole, requires the federal power in foreign relations to be reposed exclusively in the federal government, keeping it free from local interference.

According to the complaint, filed today in the Eastern District of California, the defendants have pursued or are attempting to pursue an independent foreign policy in the area of greenhouse gas regulation. The Constitution prohibits states from making treaties or compacts with foreign powers, yet California entered into a complex, integrated cap-and-trade program with the Canadian province of Quebec in 2013 without congressional approval.

California’s agreement with Quebec, which the Western Climate Initiative facilitates (and where the Western Climate Initiative’s board is run by California and Quebec governmental actors), interferes with the proper execution of these federal responsibilities. Accordingly, today’s complaint asks the court to uphold the exclusive role of the federal government in conducting our foreign policy by declaring the agreement — and related statutes and regulations —unconstitutional, and enjoining their operation.