（三）措施是否构成对国际贸易的变相限制
在“美国精炼汽油和传统汽油标准案”中，上诉机构认为，“对国际贸易的变相限制”需要与“武断或不正当的歧视”结合起来理解：‘Arbitrary discrimination’, ‘unjustifiable discrimination’ and ‘disguised restriction’ on international trade may, accordingly, be read side-by-side; they impart meaning to one another. It is clear to us that ‘disguised restriction’ includes disguised discrimination in international trade. It is equally clear that concealed or unannounced restriction or discrimination in international trade does not exhaust the meaning of ‘disguised restriction.’ We consider that ‘disguised restriction’, whatever else it covers, may properly be read as embracing restrictions amounting to arbitrary or unjustifiable discrimination in international trade taken under the guise of a measure formally within the terms of an exception listed in Article ⅩⅩ. Put in a somewhat different manner, the kinds of considerations pertinent in deciding whether the application of a particular measure amounts to ‘arbitrary or unjustifiable discrimination’, may also be taken into account in determining the presence of a ‘disguised restriction’ on international trade. The fundamental theme is to be found in the purpose and object of avoiding abuse or illegitimate use of the exceptions to substantive rules available in Article ⅩⅩ.[12]
综上所述，根据WTO专家组和上诉机构的解释，第20条在实践中的适用应该分两步走：第一步确定具体措施是否符合本条（a）到（j）项的要求，如果符合，则进行第二个步骤——确定具体措施是否符合第20条前言的附加条件。由此可见，成员方想要通过援引第20条来免除所采取的措施与WTO协议不符的责任是十分困难的，这一点在WTO争端解决机制实践中也有着充分地反映。
Case Study