A bill loaded with immigration politics and potential implications for highway safety has landed on Gov. Jerry Brown's desk. The legislation by Assemblyman Gil Cedillo, D-Los Angeles, would change police procedures at drunken-driving checkpoints, prohibiting officers from arresting drivers and immediately impounding their cars if their only offense is not having a license. Supporters say the bill, AB353, would impose a consistent policy statewide - some agencies confiscate unlicensed drivers' cars now, and some do not - while keeping DUI checkpoints from being turned into traps for otherwise law-abiding illegal immigrants who cannot obtain licenses. "In most parts of California,...