Homeland Security Secretary Markwayne Mullin has threatened to withdraw Customs and Border Protection officers from airports in sanctuary cities that limit cooperation with federal immigration agents. The move would effectively halt international travel, tourism and commerce though major airports in Chicago, Denver, Philadelphia, Los Angeles, New York, Seattle, San Francisco and elsewhere. This comes as the partial government shutdown at the Department of Homeland Security has entered its 54th day, with no signs that it will end before Congress returns from a two-week recess on April 14.