Since then, Washington imposed restrictions on food imports based on a legal provision, which contains protection measures in favour of dolphins, which must be complied with by both its fishing fleet and the countries whose vessels fish for yellowfin tuna in the eastern Pacific Ocean. If a tuna exporting country cannot demonstrate to the US authorities that it has complied with those standards, its government can order the embargo on all imports.

Despite the fact that Mexico has demonstrated that tuna fishing is carried out based on international standards for the protection of dolphins, Washington continued to deny entry of the food to its market. For this reason, in 2008 Mexico initiated a controversy with the World Trade Organization (WTO) in order to denounce the discriminatory practices of the Americans.

In 2011, the WTO ruled in favour of Mexico, after confirming that Mexico complied with the guidelines on the protection of dolphins. Thus, it indicated that the labelling requirements imposed on imports of Mexican tuna by the United States violated international trade regulations.

Although Washington appealed the ruling in January 2012, in May of that year the WTO determined that access to Mexican tuna exports to the US market should be allowed.

For this reason, in 2013 the United States authorities approved changes in their legislation to expand restrictions and prevent the entry of tuna exported by Mexico. Even so, the WTO determined that the reforms were insufficient because the different treatment towards Mexican tuna was still maintained.

Again, in 2016, changes to the U.S. Marine Mammal Protection Act were passed to extend import restrictions on marine products to other countries. However, that same year Mexico asked the WTO for authorization to impose trade sanctions on the United States based on the rulings in its favour.

Thus, in April 2017, a WTO arbitrator ruled that Mexico could impose trade sanctions of $ 163.23 million annually against the United States. This barely represented a third of what Mexico demanded since in its request it estimated that the damage caused to the local tuna industry was approximately $ 472.3 million.

Once Mexico announced its intention to impose sanctions on imports of US high-fructose corn syrup – part of another trade dispute between the two countries – Washington requested an exemption from WTO rules for reasons of environmental conservation.

So the World Trade Organization decided against Mexico’s measures. Representatives of the Mexican Ministry of Economy appealed the ruling after considering that their claim for trade sanctions against the United States was weakened.

Finally, in December 2018, the WTO Appellate Body considered that, in light of the latest amendments to the U.S. Marine Mammal Protection Act, any possible act of discrimination between Mexican and U.S. tuna products was eliminated.