The general rule is use disabling if the user can do something in the UI to get the privilege. Disabled means “you can do this command, but just not right now the way things are.” The “way things are” includes the current selection, so use enabling/disabling if the user has the EditEvent privilege for old objects but not for new objects. There should be a clear indication which objects are delete-able so users understand why the associated commands are disabled for some objects (e.g., if users generally know that records must be kept for 5 years, a simple Age field maybe be sufficient, perhaps reinforced with a graphic difference for records over 5 years old).
Use message boxes instead of disabling if there is no way to make the reason for the disabling clear to the user assuming they have average knowledge of the domain. Tooltips for disabled controls, BTW, are a great idea, but may not be sufficient by themselves.
Use hiding if the user never has the privilege no matter what they do in the UI given their current position in the organization (e.g., they are not an Application Administrator). It is cluttering and frustrating to use disabling or message boxes for this case. As far as the users are concerned, actions they don’t have the privilege for are not their job (otherwise they’d have the privilege), and so the associated controls should simply not exist in their UI. Documentation or organization procedure manuals may tell users how such actions are accomplished (e.g., “Your supervisor creates new events for you.”).
I’ve more details at http://www.zuschlogin.com/?p=40.
