Specifically, the Supreme Court upheld an act of Congress which provided for revocation of citizenship as a consequence of voting in a foreign election.

During World War II, he applied for admission and was admitted into the United States as a Mexican alien railroad worker.

Under oath, Perez admitted that between 1944 and 1947, he had remained outside the United States to avoid military service and had voted in an election in Mexico in 1946.

Two central holdings were these: The provision of the Fourteenth Amendment that "All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States," sets forth the two principal modes (but not the only ones) for acquiring citizenship, but nothing in the terms, the context, the history, or the manifest purpose of the Fourteenth Amendment warrants the inference of a restriction upon the power otherwise possessed by Congress to withdraw citizenship.Congress, acting under the Necessary and Proper Clause of Art I, 8, cl 18, of the Federal Constitution, may attach loss of nationality to voting in a foreign political election, since the means, withdrawal of citizenship, is reasonably calculated to effect the end that is within the power of Congress to achieve, the avoidance of embarrassment in the conduct of foreign relations attributable to voting by American citizens in such elections, and the importance and extreme delicacy of the matters sought to be regulated demand that Congress be permitted ample scope in selecting appropriate modes for accomplishing its purpose.The court reversed itself in 1967 with its decision in Afroyim v. Rusk.

It called section 401 of the Nationality Act of 1940 unconstitutional and stated that the Fourteenth Amendment prevents Congress from taking away citizenship without the citizen's assent.