The World Trade Organization(WTO) has ruled in favor of South Korea in its challenge to U.S. antisubsidy duties on South Korean-made washing machines.

In the final ruling on Wednesday, the WTO Appellate Body said it is a breach of the international antidumping treaty if the U.S. applies the method of “zeroing,” a practice of disregarding instances when the export price is higher than the home market price.

The trade watchdog also ruled that Washington's "targeted dumping" scheme, or unfair price cuts aimed at specific regions, time periods or customer groups, is not legitimate.

The U.S. Commerce Department imposed heavy antidumping duties on South Korean washers in December 2012, using the zeroing calculation method.

In response, Seoul appealed to the WTO against the decision in August of 2013, and a WTO adjudication panel partially ruled in favor of South Korea in March.