sentences:  However, the Supreme Court did leave the door open for courts, exercising a vigorous gatekeeping function, to recognized new actionable rules based on evolving principles of international law.However, "federal courts should require any claim based on the present-day law of nations to rest on a norm of international character accepted by the civilized world and defined with a specificity comparable to the features of the 18th-century paradigms".Having set forth the relevant standard, the court evaluated whether Pfizer did in fact violate customary international law.