Advance Parole - Reasons
please check out this link
http://uscis.gov/graphics/services/Emergency/index.htm
Advance Parole
Most aliens who have pending applications for immigration benefits or for changes in nonimmigrant status need Advance Parole to re-enter the U.S. after traveling abroad. Aliens applying for advance parole on the basis of a pending application for adjustment of status must be approved for advance parole prior to leaving the United States in order to avoid the termination of their pending application for adjustment. Note: this does not apply to aliens who have applied to adjust to permanent resident status and who maintain H-1B (Specialty Worker) or L-1 (Intracompany Transferee) status, or their dependents, who have applied to adjust to permanent resident status and who have valid H-1B or L status and valid visas, V nonimmigrants who have a valid V nonimmigrant visa, are in valid V nonimmigrant status and have or obtain a valid V nonimmigrant visa before applying for readmission to the US, and K-3/4 nonimmigrants who have applied to adjust to permanent resident status and who have a valid K-3/4 nonimmigrant visa, are in valid K-3/4 nonimmigrant status and have or obtain a valid K-3/4 nonimmigrant visa before applying for readmission to the US.
Aliens in the United States should, prior to departure, obtain Advance Parole in order to re-enter the United States after travel abroad if they have:
Filed an application for adjustment of status but have not received a decision from the USCIS;
Hold refugee or asylee status and intend to depart temporarily to apply for a U.S. immigrant visa in Canada; and/or
An emergent personal or bona fide reason to travel temporarily abroad. Applicants who are the beneficiary of a Private bill and Applicants who are under deportation proceedings must file to the Department of Homeland Security, 425 I Street, NW, ATTN: Parole and Humanitarian Assistance Branch, Washington, DC 20536
Aliens in the United States are not eligible for Advance Parole if they are:
In the United States illegally;
An exchange alien subject to the foreign residence requirement;
