The World Trade Organization ruled that American "dolphin-safe" labeling requirements on Mexican tuna comply with international trade rules, siding with the U.S. in an appeal brought by Mexico and ending a 10-year dispute between the neighboring countries, the U.S. Trade Representative's Office said Dec. 14.

In a news release, U.S. Trade Representative Robert Lighthizer said the ruling caps off "aggressive litigation tactics" on the part of Mexico.

"The WTO has finally confirmed —as we've said all along— that U.S. dolphin-safe labeling requirements are consistent with WTO rules," Lighthizer said. "After more than 10 years and multiple erroneous WTO reports, the latest compliance reports have finally reached the right conclusion, ending this longstanding dispute."

The WTO first ruled in favor of the U.S. labeling requirements in October 2017 but Mexico filed an appeal at that time. The WTO's decision on Mexico's appeal on Dec. 14 brings the case to a close.

The original case dates to 2008, when Mexico filed a complaint with the WTO, claiming that the U.S. was imposing strict penalties and tests on the Mexican tuna fishing industry. The U.S. countered that Mexican fishers employ a tuna fishing method that harms dolphins through chasing and capturing methods. The USTR's Office has previously said its fishing requirements do not discriminate against specific countries.

The ruling was immediately rebuked by Mexico.

In a statement, the Mexican Ministry of Economy said the ruling does not recognize the high sustainability standards it has for its tuna fishing industry, adding that it will continue to minimize the impact on the environment.