Have you ever felt that someone is using something they own in a way that they shouldn't, but then realized that since they own it they actually have a right to do whatever they want with it as long as it's not interfering with other people's rights? Well, most likely, your original feeling was right. The rationale is that even if you own something, there are such things as positive duties, so it's still a sin to use it in certain ways. And if you sin, then you deserve to be punished, which may come in the form of others disobeying your decrees regarding your property.
Example: The computer belongs to John. Sally needs to use it for her studies (and John isn't using it), but he decides that she can't because he feels territorial about it. Due to the above reason, she is justified in taking it and using for her studies, even though it isn't hers and she has no right to it, because John deserves it.