台灣與日本在東海海域重疊引發爭端，然現階段可處理者僅限於海域生物資源養護與管理問題，台日雙方雖就漁權持續協商，但遲遲未能有所突破，台灣遂於2003年11月正式核定「中華民國第一批專屬經濟海域暫定執法線」，作為執法依據以確保漁權。本文試圖從國際法角度析論此一執法線之可能法律根據，本文首先介紹暫定執法線之基本背景與認知，其次深入探討重疊海域劃分國際法規定，亦即劃界必須根據國際法以協議劃定，達成公平解決，若無法達成協議，則可做出臨時安排，但此臨時安排不能妨礙最終協議之做成。台日雙方若能夠以法律規範處理重疊海域議題，則其適用規範，應是專屬經濟區海域生物資源養護與管理，以及劃界相關規範。接著本文並就本案劃定界限時所需考量因素之適用進行分析與評估，包括相向海岸線長度比例、社會經濟因素及政治考量，台灣基於上述理由，並考量客觀相關因素，最後取海岸線長度比例為衡平修正的因素，連結出簡單直線，作為第一批暫定執法線。文中主張基於睦鄰之考量，該執法線僅是暫定《聯合國海洋法公約》第56條賦予沿海國海域主權權利之範圍，目的在作為雙方未來得以相互理性處理劃界爭端之基礎。

Several disputes remain regarding the overlapping maritime claims of Taiwan and Japan. One area currently under consideration is the conservation and management of living resources in these overlapping zones. Although the two sides are presently engaged in talks on fishing rights, in November 2003 Taiwan, fearful of no imminent breakthrough, approved the First Set of Republic of China Exclusive Economic Zone Provisional Law Enforcement Lines of the Republic of China with an aim to enhancing Taiwan's negotiation position. This article tries to analyze the legal basis of this set of lines from the view of international law, beginning with an introduction to the basic context and content of the publication of the set of provisional law enforcement lines, followed by a more detailed explanation of international law rules for the delimitation of overlapping maritime claims. Any such delimitation must be reached by agreement between the parties in accordance with international law with a view to achieving an equitable result, failing which provisional arrangements can be made, which must not hinder a final resolution. If Taiwan and Japan are to come to an agreement regarding their overlapping maritime claims and the limits of legitimate activity therein, it will probably be on the conservation and management of living resources in the Exclusive Economic Zone. This article will then provide an analysis and evaluation of the factors influencing the provisional lines as set by Taiwan in this case, including coastal length ratio, and social, economic and political factors. Based on the reasons cited above and on an objective contemplation of the relevant considerations, Taiwan has employed a simple baseline as a provisional set of lines, balanced by the proportional length of the two parties' coastlines. This provisional measure not only lays out the extent of the sovereign rights afforded to coastal states by Article 56 of the United Nations Convention on the Law of the Sea, but also provides a basis for the rational and mutual resolution of maritime delimitation issues between the parties.