Certificate of Airworthiness or Permit to Fly
S10 4.17.2 Each competing aircraft must possess a valid certificate of airworthiness or permit to fly not excluding competition flying. This document must be issued or accepted by the country of origin of the aircraft, or the country entering the aircraft, or the country of the organisers.
This text is a problem for aircraft (especially paramotors) when they are deregulated under national rules and no Certificate of Airworthiness or Permit to Fly is required.
For the time being this is just a note that these references need review.