The Roman Catholic archdiocese in Chicago told its schools this week not to let federal immigration agents into their buildings without a warrant, in step with guidance given to hundreds of Chicago public schools last week in response to President Donald Trump’s efforts to crack down on illegal immigration. Marking what may be the first such guidance issued by a Roman Catholic church leader, Cardinal Blase Cupich sent the directive in a letter Monday to principals of more than 200 schools and other officials in the nation’s third largest archdiocese.