The decision overturned the lower court opinion, which said that the US government was bound by the foreign interpretation, as long as the interpretation was reasonable.
In Animal Science Products, Inc v. Hebei Welcome Pharmaceutical Co., four US companies sued a Chinese pharmaceutical company for fixing prices on vitamin C in violation of the Sherman Act [text]. The defendant said that since the Chinese government required them to fix prices on vitamin C, the company could not be held liable.
Writing the unanimous decision, Justice Ruth Bader Ginsburg wrote that "a federal court should carefully consider a foreign state's views about the meaning of its own laws." She continued, "But the appropriate weight in each case will depend upon the circumstances; a federal court is neither bound to adopt the foreign government's characterization nor required to ignore other relevant materials." This is consistent with Federal Rule of Evidence 44.1 [text], which directs the court to "consider any relevant material or source" when interpreting a foreign law.