I fully support their right to secession, as a semi-southerner and states rights supporter! I welcome Good ‘Ole Bernie (and Howard “The Duck” Dean’s) Exit from the US!
I think you guys should strip them of US citizenships at independence. And then require visas to enter the United States. Erect stringent border controls on both borders and subject every one of them 3-hour interrogations and searches each time they enter the United States.