Ronnie-

I didn't take your post to be argumentative, just seeking the bottom line. AMA could help clear this up, just by correcting a transcription error that's been hanging around for more than a quarter of a century.

An AC in FAA's realm is pretty much in line with what you cited from the legal arena. When AC 91-57 stood alone as 'the word' from FAA, compliance was clearly voluntary. The potential consequences of non-complying voluntarily are hinted at in the text of that document: FAA might find a reason to regulate model aircraft if people don't voluntarily comply.

In a sense one could argue that compliance with AC 91-57 is still voluntary, but the way it is invoked in UAS_Policy_05_01 means that there are different consequences for non-compliance. The definition of model aircraft in the UAS Policy includes operation in conformance with the AC. IOW, if you aren't conforming to the restrictions in the AC, you are operating a UA that is not a model aircraft as they defined it, and so are not exempted from the general regulations of UA delineated in the UAS Policy.

As for whether FAA policy has the power of Fed law behind it, I'm not going there except to suggest that you not come to a final conclusion before doing further research. FWIW, I won't be operating an uncertificated UA in the National Airspace. At least I will endeavor not to get caught at it........

Abel