Hi Jarkko,
This is the expected behaviour from what I know. I believe the tcl cr api should be able to handle this. Normally its up to the developer to either unpublish the items first and delete it, or the UI will inform the user that its not able to delete since other users are still using, viewing, etc..
If you are talking about the associated items, I think the relationship must be removed first before deleting the items.
