The problem is that for Plugins like Changes Bar that create and maintain read-only changelists, if they are removed the changelist persists (it is stored in iws) and cannot be deleted. Dmitry Jemerov suggested such an api, and mentioned it would be useful in Perforce integration too. For further details pls check out http://www.intellij.net/forums/message.jspa?messageID=5195011#5195011 and replies.