After the WTO was established, the traditional criterion of the necessity test was replaced by a new one. In a series of cases, with regard to“necessity”criteria of measures, the dispute settlement body first determined the level of protection only after reviewing the existence of lower trade restrictions as reasonably available alternative measures, and introduced the concept of trade-offs to help determine whether WTO members could be expected to implement other alternative measures of lower restrictions. The factors to be considered include the contribution of measures on the target, the restriction degree of the measures and the importance of value desired to be protected