This paragraph from the Tuna panel report seems like it could have some relevance for the Seal Products dispute:
7.442 As established above, the US dolphin-safe provisions aim at protecting dolphins. That this particular piece of legislation does not afford protection to other animals or marine species should not be sufficient reason to consider the goal of the measure to be illegitimate. As the Appellate Body has recognized, "certain complex public health or environmental problems may be tackled only when a comprehensive policy comprising a multiplicity of interacting measures". The United States has indicated that its measures are part of a comprehensive policy to protect dolphins. Moreover, Mexico has never argued that the US dolphin-safe provisions are the only instrument the United States has put in place to protect marine life. It would be highly implausible to expect that a single regulatory instrument should serve all the purposes that may be legitimately pursued by the Members. Therefore, the Panel does not consider that the objective of contributing to the protection dolphins of the US dolphin-safe provisions should be considered illegitimate because it does not cover the protection of other marine species.