A Databricks account administrator can disable account-wide access to the Personal Compute default policy using the following steps:

1. Navigate to the Databricks Account Console.
2. Click the “Settings” icon.
3. Click the “Feature enablement” tab.
4. Switch the Personal Compute setting from “Enable for all” to “Delegate”. This delegates access to the workspace-level ACLs of the policy.

Now users cant create personal compute from cluster UI, but still they can create personal compute from notebook.

You can create a Personal Compute resource from a notebook in only three steps:

1. At the top of your notebook, click the Connect button.
2. Select Create new resource…. This will open a dialog that defaults to the Personal Compute policy.
3. Click Create.

Once your Personal Compute resource is running, your notebook will connect to it automatically.