Employees should be unable to delete their own holiday

We would find it useful if employees couldn't just delete holiday from their planner, but instead request holiday to be deleted through their manager. For example, we add some holiday dates for christmas office closure, however employees can still delete these if they wanted to, causing issues with holiday allocation. If employees required approval to delete holidays, or if there was an option to lock admin added holidays so employees couldn't delete them, that would be great.