I know that a lot has been discussed around this issue, and it really has turned entertaining.
I've asked questions concerning this issue to a friend of mine, who, by his own admission is far from an expert on firearms law or AWB94, but did have this to offer. Makes for interesting reading!
Originally emailed to Eric from a Silver Tongued Lawyer Type Friend:
[size=4]I did some hunting to determine the strength of an ATF opinion letter. Of course it is not in and of itself binding law. It is merely an "interpretive rule" (a non-legislative rule) interpreting the individual provisions of the Crime Bill (or what ever statute is at issue in a particular opinion letter). Agencies make law in basically two ways: rulemaking (formal and informal) and adjudication (formal and informal). Rulemaking is a lot like legislating, and adjudication is a lot like what courts do. I haven't checked the ATF's statutory mandate (the statute that actually created the ATF) and I haven't checked the Crime Bill for authorization, but, presumably, the ATF is authorized to promulgate legislative rules (rulemaking, which produces "regulations") regarding the Crime Bill and authorized to conduct adjudications regarding specific individuals (I'm less certain on this one). This means the ATF could either issue a legislative rule that outlines how pre-ban receivers lose their pre-ban status. Then anyone possessing a rifle in a pre-ban configuration that actually is built on a pre-ban receiver that lost its pre-ban status would be guilty of violating the Crime Bill. Or the ATF could simply charge an individual (adjudication) with violating the crime bill for possessing a rifle in a pre-ban configuration that is built on a receiver the ATF deems to have lost its pre-ban status under their interpretation of the Crime Bill. In that event, either the ATF would conduct a hearing (as noted above, I'm not sure whether the ATF is authorized to hold adjudicative hearings), or a federal prosecutor would simply charge the crime in a court of law and the ATF's interpretation of the Crime Bill would be used by the court when applying the Crime Bill to the facts of the case. The scary thing is that, although some people have argued for a criminal law exception, where a statute is ambiguous and an agency has issued a legislative rule interpreting that statute or held an adjudicatory hearing wherein the agency interprets that statute, courts apply something called [i]Chevron[/i] deference, where the court only looks to see if the agency's interpretation is "reasonable" (actually, this is the second step in Chevron deference--the first step is determining whether the statute is ambiguous). This standard is highly deferential to the agency's determination. Where the agency has not issued a legislative rule or held an adjudication, but has instead issued an interpretive rule (such as ATF position letters), the courts apply a slightly less deferential standard (known as [i]Skidmore[/i] deference). This standard is nonetheless fairly deferential to the agency. In effect, un-elected agencies have some power to effectively promulgate criminal law. This means you and I can be held criminally liable under rules created by some dumb federal agency, comprised by people that neither you nor I elected. If you're still reading at this point, then kudos.[/size=4]
Other Lawyers, please feel free to comment.