General Motors and daimlerChrysler were set to announce Tuesday that they werre dropping law-suits against the state of California over a landmark clean-air regulation that required the production of millions of low-emission cars and trucks over the next decade and a half. The move is a temporary but momentous environmental truce between the auto industry, which hs successfully blocked the Zero Emission Vehicle mandate that was set in motion in 1990, and california, which wields enormous influence oveer the global industry.