The Monopoly Regulation and Fair Trade Act(hereinafter‘MRA’) reguires‘unjustness or lack of justifying factors’, o‘r anti-competitiveness or unfairness’in order to establish the illegal acts of collaboration, merger, abuse of dominance, and unfair trade practices. Only the main clause of the article 29 (1) stipulates that resale price maintenance(hereinafter‘RPM’) is prohibited, not requiring any normative factor. The same provision allows maximum RPM to be legal by relying on the exception clause. This raises the interpretive issue whether exceptions can also be allowed to the minimum RPM.In order to solve the issue, we should first clarify what the reason for prohibiting resale price maintenance is. Some argues that it is prohibited because it coerces other enterprises’ will. This opinion finds its ground in article 2, paragraph 6 in that the concept of‘forcing or binding’is used to define RPM. However,‘forcing or binding’here simply means ‘effectively enforceable’or‘not just being the expression of hope’, and not necessarily means ‘mandating involuntary acceptance’. The decision of the Supreme Court of Korea, 99두 11141, also finds the meaning in this way.Under the market economy where‘freedom of contract’is guaranteed, accepting others’ request is just part of voluntary contract or trade, in consideration of getting corresponding benefit from the other party in return. Therefore,‘forcing or binding’the level of resale price in article 29 (1) should be understood as suggesting voluntarily acceptable condition unless proved otherwise. This leads us to the finding that the reason for RPM to be prohibited lies in its possible‘anti-competitive’effect. In other words, it is prohibited because RPM limits the degree of price competition on distributional level.If RPM is prohibited because of its anti-competitiveness, whether or not we should allow exceptions for minimum RPM will depend on whether it can bring any pro-competitive effect. Scholars have agreed that minimum RPM can have pro-competitive effect. Furthermore, in Leegin case of 2007 the Supreme Court of the U.S. held that it would change the approach to minimum RPM from per se illegal to rule of reason. This implies that the pro-competitive effect of minimum RPM is not ignorable. According to Leegin, the illegality of minimum RPM should be decided after considering both the intra-brand anti-competitive effect and the interbrand pro-competitive effect.Considering the possible pro-competitive effect of minimum RPM, it would be unconstitutional if we totally ban the conduct without any exception. More specifically, first it would infringe the freedom of businesses by excessive prohibition; and second, it would infringe the right to equal treatment since other violations under the MRA allow justifying factors. The exemption under the article 29 (2) is only open to a certain scope of products, still remaining the issue of unconstitutionality. Foreign competition laws of the U.S., EU, and Japan also allow minimum RPM to be justified when its final effect is pro-competitive.Therefore, it would be desirable that we add an exception clause explicitly for the minimum RPM in article 29 (1). However, even under the current statute the main clause of article 29 (1) should be interpreted in the way that minimum RPM is allowed once its procometitiveness is proved. This interpretation would make the provisions of the MRA harmonized each other, and conformed to the constitutional principles. Additionally the following arguments support this way of interpretation: first, the Supreme Court of Korea held in its 89다카29075 decision that‘unjustness’was required to establish RPM when there was no exception clause at all even for maximum RPM; second, the current conditional clause for maximum RPM can be interpreted as an exemplification, and not denying its possible application to minimum RPM when there is certain pro-competitive effect; and third, the enforcement results under the interpretation shall not be unreasonable. Whereas the U.S.' rule of reason approach can bring the result close to‘per se legal’, the conditional clause of Korean law shall treat the minimum RPM anti-competitive until enterprises prove the procompetitive effect.