Legal contracts get their teeth from the contract law on which they rest. If you and I sign a contract whereby I promise to deliver a service or a product for compensation, you can point out to me if I don’t deliver to the agreed upon specification, and I can then do right by you. However, if I still don’t respond satisfactorily to your request for emends, or if I have my own beef with the performance of your reciprocal contractual obligation, we can go to the court and get a judgment. It is this legal fallback that gives the contract any meaning, for without the law the contract would be toothless. However, involving lawyers and police officials at every interaction would too make life really
brutish and short.
Contract law, in the United States, is a state-level law. But while its exact specifications may vary from state to state, generally for a contract to be valid, it involves two parties of sound mind to agree on the terms. The word contract itself traces its roots to
Old French contract, now contrat = Provençal contract , Italian contratto , < Latin contractus (u- stem), < contract- participial stem of Latin contrahĕre to contract v. Formerly conˈtract. (OED 2015)