You can *only* withhold another's property if there is a written agreement giving you a security interest in that property for a debt or obligation, or otherwise allowing you to offset it vs. amounts owed you. In the absence of such an agreement, you have no right to withhold, take, etc. their inventory; if you do, not only could they sue you its value, but since what you will be doing is theft, they could file criminal charges against you, too.