大法官在釋字第三二九號解釋中，以「重要性理論」作為判斷立法院於條約締結事項有權參與程序範圍的標準，依此標準幾乎所有國際協定均須經立法院審議。然而對外事務性質特殊，立法者對其他國家的行為無規制力，且涉外事務與時遽變不具可預測性，採合議制的立法院對此難為即時反應；行政機關基於機動、彈性、效率的特性，從功能最適的觀點，較國會更適於主導對外事務。據此，有必要探討「重要性理論」於對外事務領域的功能與意義，與其適用於內政領域時有何異同？行政與立法兩權於對外事務領域應如何分立與制衡？此外，立法院就對外事務時是否適宜以其常用於國內事務之法律形式為監督參與？理論上與實務上就國會監督對外事務有否發展出法律以外之參與形式？基於民主原則固然導出立法院亦有權參與重要對外事務的要求，但應如何考量涉外事務之性質來調整會參與之密度？於我國憲政體制下，是否可能在對外事務領域內承認特定不受國會監督的「行政保留」空間？釋字第三二九號解釋就上開問題均未揭示，故本文以此為研究主題，以觀察「重要性理論」在德國如何被適用於內政與對外事務領域，作為思考相關問題於我國憲法體制下應如何解決的參考。
This research project aims at the application of essentiality theory (Wesentlichkeitstheorie) in the field of foreign affairs. The essentiality theory is a concept originally from Germany and used by Judicial Yuan in the interpretation of No. 329 to define which international agreement should be sent to the Legislative Yuan for deliberation. The subject bases upon the doctrine of separation of powers, compares the Executive-Legislativ relationship within foreign affairs in German and Taiwan. This article focuses on whether there are differences between the application of essentiality theory in the internal and external sector. Then the author figures out the criteria to determine what is “essentiality” in the foreign affairs sector. The author claims whether the Executive Reservation can be recognized depends upon how the Constitution allocates the Legislative and Executive Powers. The essentiality theory regulates not only to which extent, but also the intensity parliament should have a determining influence on foreign affairs. This article develops some parameters to point out the required intensity of parliamentary control. Furthermore, the author explores approaches developed in german and taiwan parliamentary practice besides the form of law to supervise foreign affairs.
