In a published decision, the Fourth Circuit has rejected the Board of Immigration Appeals' limitations on the use of nunc pro tunc adoption orders to establish the citizenship of adopted children. The court held that an adoption order is effective for immigration purposes on the date that the state court order states that it is effective, regardless of the date it was filed or whether or not the state adoption statute specifically authorizes nunc pro tunc adoption orders. The court recognized that adoption matters are within the expertise of state courts, and that there is no indication that Congress meant to give the Board of Immigration Appeals the ability to override or deem invalid a state court adoption order.
The full text of Ojo v. Lynch can be found here: http://www.ca4.uscourts.gov/Opinions/Published/151138.P.pdf