By definition a contract is an exchange of promises between two parties.  John Locke wrote that in a Social Contract, the people give up some of their rights to the government in order to maintain order.  He never say that the government gives up anything. Therefore the government did not exchange anything with the people, for them  having to create compromise.  A 'Social Contract' as used by John Locke can not be applied to the definition of contract, because it is not one.