The role of law in market is to reinforce common understandings about agreements within society. In market societies, when there is tension between these two, it becomes necessary to adjust the premises of the law, in order to bring them into harmony with social expectations. This book discusses civil remedial problems related to "opportunism" in Mongolia as one of the legal transitional problems. The word "opportunism" refers to legalistic opportunism where a party breaches the agreement with impunity predicting that the court will not recognize or enforce a particular agreement. The author examines availability of substantial law relief and judicial role to disgorge opportunistic gains. This work criticizes excessively formalistic approach of Mongolian judiciary, where court decisions are consistent with letter of the law, but diverged from the public understanding of social realities. So far private agreements becomes more unstable, rather than less so, by providing incentives for opportunistic behavior that is harmful for society as a whole. Thus this work has raised the possibility of the exercising discretionary power by the courts to avoid such counter-productive judgments.