Following up from this question - or more specifically Brian Drummond's comment on the accepted answer:
Or even revoked without modification, if something new is discovered about the existing components (e.g. failure modes)
When B737 Max were grounded due to suspected issues with MCAS, what happened to the Certificates of Airworthiness of individual aircraft? Technically speaking,
something new [has been] discovered about the existing component
Per the quoted comment, this could result in the certificates being revoked. Did it actually happen? If not, what formal measures exist that prevent somebody flying a B737 Max? (Other than common sense of course.)