The Secretary of Homeland Security, in conjunction with the Attorney General and the Secretary of Health and Human Services, shall use all necessary means to ensure that each unaccompanied alien child (as defined in section 462(g)(2) of the Homeland Security Act of 2002 (
6 U.S.C. 279(g)(2))) who was removed from the care and custody of a parent or legal guardian by a Federal official or employee at or near a port of entry, or within 100 miles of a border of the United States, is reunited with the parent or legal guardian at the earliest possible date, unless one of the following has occurred: