The World Trade Organization has ruled in favor of Mexico in a trade dispute with the U.S., saying Washington's requirement for "dolphin-safe" tuna labels is unfair to Mexican fishermen.

The WTO said U.S. labeling rules set different requirements depending on where a fish is caught. It said Friday that the result is "less favorable treatment to Mexican tuna products."

A WTO appellate body reviewed the original ruling of a panel set up to settle the dispute first brought by Mexico in 2009. Friday's ruling said U.S. dolphin-safe labeling for tuna products still does not meet the requirements set by the dispute panel.

Mexico originally argued that U.S. "dolphin-safe" labels were illegal because they restricted trade. Mexico says its tuna production meets international standards preventing accidental capture of dolphins in nets.