This paper consists of three parts, each one being meant to facilitate fruitful communications among economists and legal scholars. The first part is devoted to the clarifications of the basic concept of Pareto efficiency vis a vis the related but distinct concept of social optimality which is defined in terms of the Bergson-Samuelson social welfare function. In addition, some remarks are made on the way how we should interpret the basic message of the fundamental theorems of welfare economics. It is claimed that the fundamental theorems are fruitful characterization of what the perfectly competitive price mechanism can do at equilibrium under ideal conditions, but they fall much short of justifying the use of actual competition in promoting human well-being in the market economy. Such a justification. if any. should be found elsewhere. The second part presents some basic values other than the Pareto efficiency such as equity and social respect for individual rights. It is emphasized that there are two alternative methods for articulating these values, viz., the consequentialist method and the non-consequentialist method. Depending on the choice we make between these methods in articulating values other than the Pareto efficiency, the meaning and relevance of the basic conflicts between values as typified by the equity-efficiency tradeoff or the conflict between welfare and rights become conspicuously different from each other. The third part turns attention to the concrete context in which we may illuminate some of the abstract points made in the paper. For this purpose, we have chosen the context of competition law and competition policy. It is claimed that the competition law is the basic design of the fair market game, but it should be constantly subject to the monitoring by competition policy authority so as to adapt to the changing economic environments.