Four major truck manufacturers, including Daimler and Volvo, have filed a lawsuit against the state of California to block the enforcement of the state's strict vehicle emissions standards. These standards, which aim to promote zero-emission trucks, were declared void by U.S. President Donald Trump in June. The legal action reflects the ongoing conflict between California and the federal government over environmental regulations. Additionally, the Federal Trade Commission has announced the closure of its investigation into several truck and engine makers following the end of a pact on zero-emission trucks among U.S. truck manufacturers.