This article argues that an agreement on the proper law of a contract is not a free-standing promissory term but merely has the effect of a presumption that the express choice is the proper law. If this iskept firmly in view, there are more similarities than differences between the nature of the proper law of a possibly unformed contract, the floating proper law, and the changing proper law. In all cases,reliance may be placed on an express choice of law unless it would be substantially unjust to thenon-relying party or would occasion him substantial hardship.