The Clinton Administration of the US imposed the Pelly trade sanction on Taiwan in 1994-95, on the ground that Taiwan did not comply with the CITES ban on international commercial trade of rhinoceros products. Interestingly, although Taiwan is not a Party to the CITES treaty regime, Taiwan remains to be the only country that was actually sanctioned by the US under its Pelly Amendment, a domestic mechanism designed to 'give teeth' to the implementation of the CITES. Given the US Pelly Amendment’s prominent role in enforcing international conservation programmes such as the CITES, clarification on the legality of the Pelly Amendment enforcement seems necessary. And with the widespread membership of the WTO, disputes relating to the Pelly trade sanctions would most likely to be challenged under WTO's compulsory dispute settlement mechanism. Against such a background, this article deals with the legality question of the US Pelly trade sanction under the relevant WTO rules.