Perez v. Brownwell

In 1958, a divided United States Supreme Court upheld these decisions because Perez "became involved in foreign political affairs and evidenced an allegiance to another country inconsistent with American citizenship, thereby abandoning his citizenship."

Two central holdings of Perez v. Brownell found that

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.