Currently, the UI (e.g. Akonadi Console, "Folder Properties" on a calendar) offers no option to mark a calendar as read-only, i.e. to disallow changes or removal of events or adding new events. This should be implemented independent of the backend, irrespective of whether it is a local calendar or a DAV resource.

Background: in my groupware server account, I have several calendars: one for events I maintain (add/edit events) and several that are subscriptions to external calendar feeds which are read-only. Either the groupware server does not relay the information which calendars are read-only, or Akonadi does not interpret this information correctly. At least in KOrganizer, changes can be made to calendars that are technically read-only.
To block those changes, the user should have the choice to mark a calendar read-only even if changes are technically possible, e.g. to avoid accidental changes to calendars.

The Folder Properties dialog has a "ACL" tab, but it warns to make changes here. Even if my request can be "solved" by making changes here, it sounds like a dangerous path and it deters users from making the changes. Instead, there should be a simple checkbox in the "General" tab next to the "custom icon" setting that allows the user to make the calendar read-only (or not).