Laurence Terrazas (plaintiff) was born in the United States to a Mexican citizen. While a student in Mexico, he applied for and received a certificate of Mexican nationality. To obtain this certificate, he had to swear an oath of obedience and submission to the Mexican Republic, and expressly renounce his United States citizenship. After discussions with an officer of the U.S. Consulate in Monterrey, the Department of State issued a certificate of loss of nationality. Terrazas then brought suit in district court against the Secretary of State for a declaration of his United States citizenship. The trial court found that the government had proved by a preponderance of the evidence that Terrazas had voluntarily relinquished his United States citizenship. The court of appeals reversed, holding that under Afroyim v. Rusk, 387 U.S. 253 (1967), that Congress had no power to legislate the evidentiary standard and that the Constitution required clear and convincing evidence. The Supreme Court granted certiorari on the Secretary’s appeal.