The appeals body of the World Trade Organization has dismissed an appeal from Washington over a dispute the US has with Mexico over tuna labelling.

The decision, issued on Friday (20 November), upholds an earlier ruling that found US rules on dolphin-safe tuna labels unfairly treated products from Mexico.

Friday's announcement marked the latest stage in a dispute that started in 2008 when Mexico alleged US regulations on dolphin-safe tuna broke WTO rules.

The dispute arose due to the way tuna was fished in the eastern tropical Pacific, where Mexico harvests much of its tuna. Millions of dolphins were killed from speedboats being used to herd the animals and large purse seine nets were used to catch tuna.

International standards were introduced, which cut the numbers of dolphins killed. Mexico claimed the US certification was there discriminatory and unnecessary.

In 2012, the WTO appeals body found in favour of some of Mexico's claims but not others. By the summer of 2013, the US said it had amended parts of its regulations to bring the rules into compliance with its WTO obligations.

However, in November of that year, Mexico requested another compliance panel on the amended regulations. The compliance panel issued its report this April. It argued US rules on certification, tracking and verification were inconsistent with WTO regulations. Washington disagreed with the findings and launched an appeal.

Nevertheless, on Friday, the appeals body said: "The appellate body concludes the United States has not brought its dolphin-safe labelling regime for tuna products into conformity with the recommendations and rulings of [the WTO's dispute settlement body]. The appellate body recommends that the DSB request the United States to bring its measure, found in this report, and in the panel report as modified by this report, to be inconsistent with the TBT Agreement and the GATT 1994, into conformity with its obligations under those agreements."