Since the description of the Collision Regulations for narrow channel does not cover all specific situations, substantial applications may be contested in many respects. For example, in situations where ships sailing on narrow channels intersect with vessels outside the channel, questions could arise as to whether rule of narrow channels will be applied or if rule of crossing will be applied. The judgements of the Queen`s bench and Court of appeal on the Alexandria 1 v. Ever Smart case in 2018 was of great significance in that it has come to the conclusion that a universal solution to this problem, the rule of narrow channel should be applied if even one vessel is on a narrow channel. On the other hand, the Daejeon High Court's judgment on the "Hallim Ferry 9 and Minho Collision" in 2017 is not much different from the above judgements on appearance, but the structure of the argument is different and does not seem to have made a ruling that is a guideline in the future. In this paper, I will examine in terms of legal argumentation theory how the process of justifying the navigation application of narrow channels in the crossiong situation between ships in the vicinity of narrow channels was different. Although both courts reached similar conclusions, the lack of justification is pointed out in that the Korean courts failed to provide a reasonable basis for argument. The purpose of these discussions is not to reveal which navigation rules are correct in special circumstances, but to suggest a desirable direction for providing evidence for the judgment.