In this FAA UAS risk analysis they state unambiguosly that AC 91-57 MUST be complied with for model aircraft (recreational UAVs). So much for all that "it is a request not a law" arguement. Apparently the AMA rules have been telling people to break the law for the last 30 years.
"Unmanned aircraft flown for hobby purposes or
recreation. Model aircraft must comply with
Advisory Circular (AC) 91-57, Model Aircraft
Operating Standards, published in 1981"