“

The Government must either :( 1) detain them,( 2) return them to a contiguous foreign nation, or( 3) parole them into the United States on an individualized, case-by-case basis, these options operate in a hydraulic relationship : When it is not possible for the Government to comply with the statutory mandate to detain inadmissible aliens pending further proceedings, it must resort to one or both of the other two options in order to comply with the detention requirement to the greatest extent possible.