Complex sentence: The WRSTC restricts its membership to national or regional councils comprised of the individual training organizations who collectively represent at least 50% of the annual diver certifications in the Member Council's country or region.
Split into simpler sentences: The WRSTC restricts its membership to national or regional councils. These councils consist of individual training organizations who collectively represent at least 50% of the annual diver certifications in the member council's country or region.