International dispute practitioners are well aware of the challenges that arise when the substance of foreign law is disputed in U.S. courts. Most practitioners are aware that the question is governed by Rule 44.1 of the Federal Rules of Civil Procedure, the text of which affords a U.S. federal court significant discretion and latitude in determining the substance of foreign law. When foreign law is placed in issue, however, the government whose law is at issue may seek (or be called upon) to offer its own views. The question of how much deference to afford a foreign government’s view of its own law had become a contentious issue in U.S. litigation, particularly in cases—including cases against a foreign sovereign or one of its instrumentalities—where the foreign state has an interest in the outcome of that determination.

On June 14, 2018, the United States Supreme Court decided Animal Science Products, Inc. v. Hebei Welcome Pharmaceutical Co. Ltd., a case arising from a class-action suit brought by U.S. based purchasers of vitamin C (the U.S. purchasers) against four Chinese companies that manufactured and exported the vitamin. The plaintiffs accused the sellers of fixing the price and quantity of the nutrient exported to the United States. The sellers’ primary defense was that Chinese law mandated that they fix the price and quantity of vitamin C exports.