Security exception has grown increasingly prominent since the establishment of World Trade Organization（WTO）in 1994.It is incorporated by reference to the similar article in the General Agreement on Tariffs and Trade（GATT）1949 and the International Trade Organization Charter earlier.Security exception in WTO legal system covers the areas of trade in goods,trade in services and intellectual property right which permits members exempting from the obligations under the international agreements out of the protection of its essential security interests.Considering that Article XXI of GATT 1994 in relation to trades in goods is the earliest security exception and the most controversial one in current WTO legal system,this thesis will focus on Article XXI of GATT 1994 other than security exceptions prescribed in the General Agreement on Trade in Services（GATS）and the Agreement on Trade-Related Aspects of Intellectual Property Rights（TRIPS）,especially when the text of these security exceptions are almost the same.The text of Article XXI of GATT 1994 was firstly drafted in the 1940 s as the original version of security exception in international law and remains vague,ambiguous and controversial ever since.Even though Article XXI of GATT 1994 enables members escape from obligations for national security reasons,the number of cases invoking Article XXI of GATT 1994 is relatively lower than other exceptions.However,recent years has witnessed an obvious surge on the number of trade restrictive measures invoking Article XXI of GATT 1994.Article XXI of GATT 1994,as a representative article of security exception,reflects the balance between trade liberalization and national sovereignty.Even though the drafters tried to blur this sensitive balance by ratifying vague language at the beginning,such vague drafting calls for clarification given that more and more disputes relating to Article XXI of GATT 1994 are brought before the Dispute Settlement Body（DSB）.The fact that the text of Article XXI of GATT 1994 stays the same for nearly seventy years has reveals the resistance and difficulties of amendments to it.Accordingly,this thesis strives to clarify the application rule based on the existing clause in order to resolve the increasing disputes in relation to Article XXI of GATT 1994.This thesis consists of five chapters.Chapter one introduces the existing security exception in WTO legal system,the drafting and negotiation history,the current text and structure of security exception in GATT 1994 and corresponding attributes.Among three paragraphs of Article XXI of GATT 1994,the most easily abused one is Article XXI（b）.Consequently,Article XXI（b）becomes the topic of the subsequent analysis.According to the text of Article XXI（b）of GATT 1994,there are three preconditions prior to the invocation,namely（i）the invocation must be out of the protection for essential security interests,（ii）the trade measures taken must be necessary for such protection and（iii）the invocation must be under one of the three situations prescribed in the subparagraphs of Article XXI（b）of the GATT 1994.All three preconditions follow the phrase of “it considers”.Different interpretations of “it considers” concern which preconditions are within members’ discretion and trigger the discussion over DSB’s jurisdiction.The interpretation of “it considers” therefore has a greater impact on the underlying balance between trade liberalization and national sovereignty compared with the interpretation of several keywords in the aforementioned preconditions.Consequently,Chapter two focuses on the balance between members’ discretion and the scrutiny of DSB in invoking Article XXI of GATT 1994 rather than going detail to the meaning of every controversial word and phrase.Noted that two substantive adjudications with respect to Article XXI of GATT 1994 were delivered by the DSB in 2019 and 2020 through the Russia – Measures Concerning Traffic in Transit Case（DS512）and Saudi ArabiaMeasures Concerning the Protection of Intellectual Property Rights Case（DS567）,this chapter combines the panel reports and theoretical analysis to clarify the boundary between members’ discretion and DSB’s objective judgment from three dimensions,that is（i）whether the DSB has jurisdiction over disputes invoking security exception;（ii）which preconditions are subject to members’ discretion based on “it considers”;and（iii）whether there is a limitation of members’ discretion.The jurisdiction of the DSB over Article XXI of GATT 1994 is the starting point for all issues,because if the DSB is deemed to have no jurisdiction as some members claim,all judgments on the invocation and the legality of such invocation will completely subject to the invoking member’s discretion,leading the standardization of the existing security exception losing most of its significance.For the dispute over the jurisdiction of DSB,this thesis holds that the DSB does have jurisdiction over cases invoking Article XXI of GATT1994 given that the Dispute Settlement Understanding（DSU）does not explicitly exclude the DSB’s jurisdiction and the sole political attribute cannot be the reason letting security exception immune from the scrutiny of the DSB.This chapter then comes to the second dimension that to what extent the phrase “it considers” covers,in other words,which preconditions of Article XXI of GATT 1994 can be determined by the DSB.By interpreting the phrase “it considers” pursuant to the Vienna Convention on Law of Treaties,it concludes that members shall have discretion in determining what is its essential security interest and what amounts to necessity in the invocation of Article XXI of GATT 1994 but whether the disputing trade measures are taken under one of three situations prescribed in subparagraphs of Article XXI（ii）of GATT 1994 falls into the DSB’s objective judgment.Considering that the phrase “it considers”grants members certain discretion,the last issue in this chapter is whether members’ discretion subjects to certain limitation under Article XXI of GATT 1994 and if so,what is such limitation.The panels in the DS512 and DS567 provide implications for this issue.The DSB claims the principle of good faith as a fundamental international principle binds on Article XXI of GATT 1994,and further demonstrates that such fundamental principle demands the invoking member to illustrate the interests relating to the quintessential functions of the states and the minimum plausibility between the disputed trade measures and the invoked essential security interests to satisfy the preconditions of “essential security interests” and “necessary”,respectively.Subparagraphs of Article XXI（ii）of GATT 1994 specifying objective event subject to the DSB’s objective judgment and have fewer controversies and disputes compared with the other preconditions determined by the invoking members.Therefore,clarify the limitation on the invoking members’ discretion is of more significance in the application of Article XXI（b）of GATT 1994.However,the latest cases in the DSB lacks sufficient discussion in the regards.Further to the discussion in Chapter two,the following three chapters aims to resolve the practical issues in limiting the members’ discretion with corresponding solution and suggestion.Chapter three resolves the lasting problem in relation to the application of the principle of good faith,which is the overall limitation on members’ discretion.However,the good faith is hard to be proved as a subjective motive especially the burden of proof is imposed on the invoking member.In order to make Article XXI of GATT enforceable and practical,this chapter provides that procedural requirements shall be established prior to trade restrictive measures taken pursuant to Article XXI of GATT 1994,such as making a written reasoning for the case invocation,reserving a reasonable period for the negotiation and compulsory consultation between both parties.By doing so,objective facts are provided as evidences to prove the subjective motives,and,on the other hand,such mandatory requirements increase the cost and decrease the attraction of taking restrictive measures for the WTO members and provides opportunities for the members to solve the conflicts through other methods rather than directly exercise trade measures.Given that “essential security interests” should be determined by the invoking members,Chapter four holds that the panels in DS512 and DS567 fails to illustrate the non-traditional essential security in the contest that the increasing number of cases out of non-traditional essential security invokes Article XXI of GATT 1994.By looking at the nature of essential security interests,Chapter four opines out that essential security interests should be absolutely indispensable and necessary regardless of the specific type of it.It is because security interests are a conception of high socialization.The meaning of security interests should be interpreted in specific social development context.In view that Article XXI of GATT 1994 has not been amended since GAAT1949 and will be hard to been amended in the future due to its political attributes,both DSB and members are unlikely to have an exhaustive list of types of essential security interests to satisfy the development of society.In this circumstance,“essential security interests” should be an open-ended conception in terms of its type.Any type of absolutely indispensable and necessary interests to a member should be given the same consideration according to the status of social development at that time but the invoking party is obliged to provide sufficient evidence to prove it.Asides from “essential security interests”,the invoking member is also granted the discretion to determine whether a trade restrictive measure is necessary for the protection of its essential security interests.Chapter five claims that the current standard of necessity is too low to restrict the abuse of Article XXI（b）of GATT 1994.It provides a flexible standard for reviewing what is necessary based on the principle of proportionate established in the application of Article XX of GATT,another exception clause in GATT.In accordance with the flexible standard,the more core interests impacted,the lower standard established amounting to “necessity”.Provided that the invoking member’s core state interests such as military or territory interests are impacted,the trade measures only need to have minimum plausible connection with such essential security interests to fulfill the standard of “necessity”.This thesis strives to clarify the application rule based on the existing clause in order to resolve the increasing disputes in relation to Article XXI of GATT 1994.Instead of interpreting every keyword of Article XXI（b）of GATT 1994,it focuses on the more influential aspects of the application of security exception,which are the division of member discretion and DSB review rights and the specific restrictions of members’ discretion.Compared with the DSB’s objective judgment,members’ discretion is more ambiguous and easily be abused.Therefore,this thesis further comes up with three practical issues in the limitation of members’ discretion and corresponding solutions based on the current application rule.