First of all, how do you define "untrustworthy"? Usually you delegate that decision to your browser vendor or OS distribution. If you no longer trust them for a specific CA, why trust them for any of the others?
Browsers may rely on the certificate store and trust settings provided by your OS. For example, Firefox always uses their own certificate store, while Chrome relies on the system.
certsimple has this guide on how to remove or distrust certificates in various browsers:
Browsers may rely on the certificate store and trust settings provided by your OS. For example, Firefox always uses their own certificate store, while Chrome relies on the system.
certsimple has this guide on how to remove or distrust certificates in various browsers:
https://certsimple.com/blog/control-the-ssl-cas-your-browser...