Agency (executive) acquiescence is expected by a federal circuit court.  A federal court gives Chevron deference to an agency interpretation when its in an area of agency expertise or when it relates to congressionally delegated "authority to the agency generally to make rules carrying the force of law."  United States v. Mead Corp., 533 U.S. 218, 226-27 (2001).   The BIA has eschewed having an deference due it in cases of criminal statutes and in fact acquiesces to the circuit interpretation of the statute in such cases.