1. Subject to paragraph 2, in these Regulations, “medical certificate”, in relation to a person driving or riding in a vehicle, means—
(a)a valid certificate signed by a medical practitioner to the effect that it is inadvisable on medical grounds for him to wear a seat belt, or
(b)a valid certificate to such effect issued by the authority having power to issue such a certificate under the law of another member State corresponding to these Regulations.