The U.S. Department of Justice filed complaints this week in federal courts in Sacramento and Rockford seeking to bar the California Air Resources Board from enforcing the state’s stringent emissions standards for heavy-duty trucks. Federal lawyers argued that the standards, including the 2023 Clean Truck Partnership requiring a share of zero-emission sales by 2035, are pre-empted by federal law after President Donald Trump in June signed resolutions voiding the waivers that had allowed California to set tougher rules than Washington. The federal action came two days after four large truck manufacturers—Daimler, Volvo, Paccar and International Motors—lodged their own suit against California, saying they are caught between conflicting federal and state mandates. Both sets of lawsuits contend that California’s requirements impose unlawful obligations on manufacturers and undermine nationwide standards aimed at providing regulatory certainty. California officials declined to comment on the litigation, but Governor Gavin Newsom has previously said the state’s tighter pollution limits are essential to meeting climate goals. California has received more than 100 Clean Air Act waivers since 1970, enabling it to pursue policies that have often become national benchmarks. Justice Department officials said the lawsuits are intended to end what they called California’s "ongoing defiance of federal law," level the regulatory playing field and preserve consumer choice. The cases add to a series of legal clashes between the Trump administration and California over environmental regulation and are likely to shape the future path of vehicle electrification in the largest U.S. auto market.