Riggers are qualified
Verify: ask for their card or get their name and confirm via certificate kept in office/trailer.
Okland
Subpart CC 2. (a) pg 57
Qualified Rigger (QR/QSP): All riggers shall meet the qualifications stipulated by OSHA for a qualified rigger and the qualifications listed in this document.
OSHA
1926.1404(r)(1)