There is a workspace setting called Enforce User Isolation that admins can enable to prevent creating or starting a cluster with the “No isolation shared” cluster access type or an equivalent legacy cluster type.
Attempting to start or restart a cluster of those types will fail.
There is a related account-level admin protection setting that affects these cluster types.
To enable Enforce User Isolation on a workspace:
Go to the admin settings page.
Click the Workspace Settings tab.
Click the Enforce User Isolation toggle.
Currently-running clusters are unaffected by changes to this setting until the cluster is restarted.