Those certificates which are required by the law with respect to safety and environment protection that the vessel is required to comply with are called statutory certificates.
Eg-SOLAS, MARPOL, STCW, MLC 2006
Certificates which are required for trading purpose. Ship’s registry certificate is a mandatory certificate however for Indian Ship’s it is Statutory Certificate. OPA’90 is a Statutory certificate for ship’s transiting in U.S waters but mandatory for other ship’s.