Massachusetts is preparing to adopt California’s ambitious zero-emission vehicle legislation, which would require 10 percent of cars and trucks sold within the state to produce no pollution. For the moment, though, the U.S. government is still bickering internally over whether California’s legislation is legal. Earlier this month, the Bush administration said California had overstepped its authority by trying to regulate not only emissions but also fuel efficiency, and as a result the Justice Department put the new standards on hold until 2005. The U.S. EPA, however, has proposed supporting a similar program in Massachusetts that calls for low (rather than zero) emissions. The agency is accepting public comment on the plan through the middle of November.