What describes an explicit action taken against a certificate holder for non-compliance with professional standards?

The term that describes an explicit action taken against a certificate holder for non-compliance with professional standards is "sanction." In the context of professional regulations, a sanction represents a formal measure imposed by a governing body to address violations of established standards or regulations. This could include penalties such as fines, suspension, or revocation of certification, reflecting a serious response to malfeasance or failure to adhere to the required ethical and professional conduct.

Other terms, while related, do not carry the same weight as sanctions. A warning typically serves as a preliminary measure or cautionary notice, indicating that future violations could lead to more severe consequences, but it does not represent an action of significant consequence. A reprimand often conveys disapproval but may not involve formal punitive measures. An injunction is a legal order prohibiting or mandating certain actions but is not specifically an action taken against a certificate holder in the context of professional regulation. Thus, "sanction" is the appropriate choice for describing an explicit response to non-compliance in a professional setting.