The WTO rules against “dolphin-safe” labels on tuna
From my reading, the WTO ruled correctly is this case. In 1990, the US passed a dolphin-protection law that added strict requirements to fish caught in US waters. The “dolphin-safe” certificate was designed with this in mind. Depending on where the fish is caught (in the "Eastern Tropical Pacific Zone" (ETP) or "Other fisheries"), there are more stringent or lax requirements. For the ETP zone, an example requirement is that a captain must receive training/certification on dolphin safe practices and also verify the entire haul of fish was caught using dolphin-safe practices. Fish caught in the "Other fisheries" are subject to less stringent requirements. Since much of Mexico’s tuna are caught in the ETP zone, they argue that they are unfairly being held up to US standards. Other countries, in “Other fisheries” zones, are held to a lower requirement. If Mexican tuna are sold to other countries, then they fulfill multiple unnecessary requirements and are at a disadvantage to other countries. Futhermore, it would segment their fishing industry into "US approved" and "Non-US approved" because certification must be applied to the entire haul of fish, not a portion of a haul.
There's a lot of text after this but the court determined this certification is unfair and is considered "less favorable treatment".Here is a pdf of the case: https://docs.wto.org/dol2fe/Pages/FE_Search/DDFDocuments/225...