 The view that contract law, in its positive expression, promotes efficient investment and exchange is hard to maintain in the face of doctrinal challenges (see, e.g., Posner 2003). “This is Not a Legally Enforceable Agreement” clauses used by parties to disclaim their intent for an agreement to be legally enforceable are not always enforced. Similarly, efforts by parties to opt out of legal duties in the pre-contractual bargaining phase, including duties related to disclosure of information, are often deemed legally ineffective (V.S.H. v. Texaco (1985)). In all such cases, the law’s reluctance to cater to parties’ preferences is not straightforwardly explainable in power-conferring or general welfarist terms. For an exploration of the degree to which the law’s mandatory constraints can be explained from the standpoint of efficiency, see Zamir and Ayres (2020).