NEW YORK—A U.S. appeals court on Tuesday threw out a price-fixing lawsuit against two Chinese companies that make vitamin C, a case that spotlighted trade tensions between the United States and China. Dismissing the 16.5-year-old case was justified because of a “true conflict” between Chinese and U.S. antitrust laws, and the potential impact on foreign relations, the 2nd U.S. Circuit Court of Appeals in Manhattan said. The 2–1 decision is a defeat for Texas-based Animal Science Products Inc and New Jersey-based Ranis Co, which claimed they were overcharged for vitamin C by Hebei Welcome Pharmaceutical Co and North China Pharmaceutical Group Corp. In 2016, the court voided a $147.8 million jury verdict the American companies had won in Brooklyn three years earlier, saying it must defer to China’s view that its laws required fixing prices and quantities of vitamin C exports. But the U.S. Supreme Court in 2018 ordered a …