SAN DIEGO (AP) — The sheriff of the nation’s fifth-largest county on Tuesday defied a new policy to limit cooperation with federal immigration authorities, setting up a showdown over a new obstacle to President-elect Donald Trump’s mass deportation plans. San Diego County supervisors voted to prohibit its sheriff’s department from working with U.S. Immigration and Customs Enforcement on the federal agency’s enforcement of civil immigration laws, including those that allow for deportations. California law generally prohibits cooperation but makes exceptions for those convicted of certain violent crimes.