You can own a means of production without government backing, but without establishing laws and implementing a means of enforcing them, there's no guarantee that someone wouldn't come along and take it by force.

I just finished a Law 101 class so I'm by no means an expert, but I think the above explains the theory behind why we need laws. Whether you think the theory is legitimate or not is up to you. When I started the course, I was surprised to learn that our entire legal system was designed around the concept of property rights.