Assuming the alien is not in removal proceedings, an appeal from a USCIS decision on an I-601 Waiver application should be forwarded to:

The appeal from a USCIS decision on an I-601 Waiver application should be forwarded to the USCIS Administrative Appeals Office (AAO). The AAO is specifically designated to handle appeals from certain decisions made by USCIS, which includes decisions on waivers such as the I-601.

When an applicant seeks a waiver, particularly for grounds of inadmissibility, and their application is denied, the AAO provides a mechanism for reviewing and potentially overturning that decision. This is critical because the AAO is equipped with the expertise and authority to evaluate the evidence, consider legal arguments, and apply relevant immigration law to the facts of the case.

The other entities mentioned, while important in the immigration process, do not handle appeals for I-601 Waivers specifically. The Board of Immigration Appeals (BIA) mainly deals with appeals from immigration court decisions and typically does not receive direct appeals from USCIS decisions unless there's a prior removal order involved. The USCIS Office of the Chief Counsel (OCC) serves as the legal advisor for USCIS and typically does not handle appeals from applicants. USCIS Headquarters oversees policy and administrative operations but does not accept appeals directly from waiver applications. Therefore, directing the appeal to the AAO is the appropriate