This paper examines US-Tuna II, one of the disputes called a trilogy of the cases (along with US-Clove Cigarettes and US-COOL) under the Word Trade Organization (WTO)'s Agreement on Technical Barriers to Trade (hereinafter "TBT Agreement"). This case was Article 21.5 (compliance) proceeding under the WTO's Dispute Settlement Understanding, addressing a question whether the United States was compliant with the findings made in the original proceeding. A major issue in this proceeding was whether the regulatory distinctions under the U.S. labelling scheme were "calibrated" to the differences in risks to dolphins among different fisheries under Article 2.1 of the TBT Agreement. This paper analyzes the treatment of the "calibration" notion under this proceeding. However, the compliance panel did not properly apply this "calibration" notion, thus, the dispute was not settled under this proceeding. Currently, the second Article 21.5 proceeding is ongoing.