[...] no one can not own a firm because a firm is a set of human agents.This seems a bit odd. It’s based on an incorrect definition of a firm. First, obviously the idea of the legal ownership of a firm is well established in most countries. Second, as people own firms and they can not own other people then firms must be something other than a group of human agents. This explains why theories, such as the property rights approach to the firm, define ownership in terms of control rights over non-human assets.
PS: If you have an interest in labour managed firms, Dow's book is a must read.
- Dow, Gregory K. (2003). Governing the Firm: Workers' Control in Theory and Practice, Cambridge: Cambridge University Press.