Common law defenses to enforceability

     A debtor may assert familiar common law defenses (e.g. fraud, duress, mistake, unconscionability) to a contractual obligation to pay. If the debtor is thereby relieved from a contractual obligation to repay debt, the seller or lender's security interest, whether in real or personal property, is not enforceable, because there is no underlying debt to secure.  We leave unexplored the question of when a debtor may have an obligation to repay grounded in restitution and, if so, whether such restitutionary obligation is secured.

     A debtor may also attack the grant of security itself on common law grounds even if the underlying obligation remains enforceable. See, e.g., U.C.C. 1-103. The classic case, decided by the United States Court of Appeals for the District of Columbia before Congress adopted the Uniform Commercial Code for the District, is Williams v. Walker Thomas Furniture.