This paper considers how promissory estoppel jobs are undertaken in two jurisdictions that ought not to need promissory estoppel. The purpose is to achieve a better understanding of systematic decisions to enforce promises and to discover the doctrinal combinations possible in mixed Civil Law/Common Law jurisdictions. This bilateral comparison allows an examination of the different philosophical and moral bases for according promises legal force, whether founded on contract and will or on delict and injury. The differing functions of formalities are also discussed. More particularly, Scotland does not have promissory estoppel but has a remarkable doctrine allowing the enforceability even of unilateral, gratuitous promises. In addition, the Scots law of personal bar, which is similar to estoppel and waiver, fulfills other jobs associated with promissory estoppel. Louisiana, on the other hand, long claimed to reject promissory estoppel but then reversed course and adopted the doctrine about twenty-five years ago. The comparison of these two legal systems affords an opportunity to observe the doctrinal mixes and philosophical choices that have long drawn comparative law scholars to mixed jurisdictions. It also reveals the roles that promissory estoppel can play and how it is not entirely tethered to the problems of the consideration doctrine.