A federal judge in California dealt a blow to the Trump administration as it seeks to invalidate the state’s cap-and-trade program.

The Department of Justice sued the state in October, arguing that California’s program to reduce vehicle emissions, done in collaboration with the Canadian province of Quebec, was akin to an international treaty beyond the scope of the powers of a state.

But Judge William Shubb of the U.S. District Court for the Eastern District of California rejected that argument late Thursday.

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“‘Treaty’ is a term of art,” Shubb wrote. “The Supreme Court has come to understand that not all international agreements ... constitute treaties in the constitutional sense.’”

The program, underway since 2013, aims to improve California’s air quality, capping emissions from the transportation sector while allowing companies to trade credits with others in the province of Quebec.

California described the agreement as a nonbinding sign of good faith, a point the judge backed, noting that each program is run independently. It also doesn’t veer into territory typically overseen by the federal government.

“This agreement is not a treaty creating an alliance for purposes of peace and war ... nor does it constitute a treaty for ‘mutual government’ or represent a ‘cession of sovereignty.’” Shubb wrote.

Two other points in the case are still being litigated.