Currently the state of an item can be changed by anybody, depending on their permited transitions, even if the item is not assigned to them.
I updated the Items's getPermittedTransitions method to restrict this change to only the user that has the item assigned to, the Admin for the space or the super user.
See attached patch
Restrict getPermittedTransitions
Sounds good. Has anybody a refutation. Otherwise I will commit the patch in the end of the week.