see, now that is what I call FAA saying otherwise to AC91-57 enforcement
So much for the FAA 400' Law.

What about the 20kg International treaty--> FAA law --> AMA rule?

"The AC encourages voluntary compliance with safety standards. The Academy of Model Aeronautics recommends a weight restriction of 55 lbs. (There are exceptions to the 55 lb. limit for operating large models.) You should follow industry-developed safety standards when operating your model aircraft. "

Sounds like the ICAO/FAA 20kg is voluntary / imaginary too (what the heck is ICAO?)