It is almost impossible today for an American citizen to lose her citizenship against her will. That was not always the case; in the period from 1940 to 1964, more than a hundred thousand individuals forfeited their US nationality. Patrick Weil's important book The Sovereign Citizen: Denaturalization and the Origins of the American Republic, rediscovers this lost history of US expatriation law and practice during the first half of the twentieth century.

The book tracks three strands of denaturalization practice. It first traces the rise of denaturalization as it reflected and facilitated the federalization of citizenship. With state courts administering naturalization, a huge wave of immigrants starting in the late nineteenth century gave rise to endemic fraud as local political bosses looked to corral new voters to the ballot box. The resulting scandals prompted the transfer of naturalization functions to federal authorities – first to federal judges, subsequently to the Bureau of Naturalization, first a shared authority with the states, then exclusively federal. Federal authorities sought to police against corruption but also to resolve the citizenship status of those who secured naturalization through fraud or misrepresentation. Some players in the federal bureaucracy took a hard line, where others – Taft's Attorney General Charles Wickersham in particular – worked to validate naturalization where errors were immaterial or where others had orchestrated the wrongdoing.

Second, the book highlights the use of denaturalization for ideological purposes. Emma Goldman counts as among the earliest and most prominent victims of ideological denaturalization, albeit indirectly through the denaturalization of her anarchist husband. Later targets included members of the Nazi-sympathizing German-American Bund, against whom the Roosevelt administration launched a high-profile, systematic denaturalization program. But federal prosecutors in the field resisted the initiative, especially as applied against rank-and-file members. The courts, meanwhile, obstructed the denaturalization of communists. Ideological denaturalization cases worked from the theory that individuals holding putatively un-American beliefs violated the naturalization oath's undertaking to abjure former allegiance and to support the Constitution. In its 1943 decision in the Schneiderman case, in which former Republican Party presidential nominee Wendell Wilkie served as legal counsel to the Communist Party petitioner, the Supreme Court raised the bar to denaturalization. By requiring “clear, unequivocal, and convincing” evidence that an applicant was not attached to constitutional principles at the time of naturalization, the ruling effectively extinguished the utility of denaturalization as an ideological weapon.

Finally, The Sovereign Citizen examines loss of citizenship in the context of connection to other states. Legislation enacted in 1907 provided for the presumptive expatriation of naturalized citizens upon return to their country of origin for a period as short as two years. This accounted for the largest numbers of those losing citizenship by virtue of post-naturalization conduct. The 1907 Act also provided loss of citizenship (regardless of how acquired, by naturalization or birth) where an individual naturalized in another country or took an oath to a foreign government. In 1940, the grounds for expatriation among both naturalized and native-born was expanded to include such activity as service in a foreign armed force as well as for the mere act of voting in a foreign political election.

The application of these expatriation measures gave rise to a series of contentious Supreme Court decisions, which Weil vividly recounts by drawing from Supreme Court and related archives. The drama reached its apex on 31 March 1958, when a deeply divided court announced its decisions in three cases. In Trop v. Dulles, the Court found the punitive use of expatriation to constitute cruel and unusual punishment under the Eighth Amendment in a case involving termination of citizenship for military desertion. In Nishikawa v. Dulles, the Court required the government to bear the burden in proving that an individual's military service in Japan had not been coerced. But in Perez v. Brownell the Court (with Justice Frankfurter writing) validated expatriation for voting in a Mexican political election. The cases provoked shifting votes and high emotion. The hapless Charles Whittaker switched sides with each draft opinion, and the newly confirmed William Brennan cast the deciding votes to reject expatriation in Trop and Nishikawa while approving it in Perez, rebuffing an agitated Chief Justice Earl Warren who had moved to an Arendtian position on citizenship's centrality. “These are the most important constitutional pronouncements of the century,” observed Justice William O. Douglas with characteristic restraint in delivering his dissent from the bench in Perez (147).

Jurisprudential instability subsided with turnover among the justices (Goldberg and White replacing Frankfurter and Whittaker) and Brennan's recanting of his position in Perez. The Court struck down the 1907 ground of expatriation for return to homeland as an unconstitutional discrimination against naturalized citizens in the 1964 Schneider decision. The capstone came with Justice Black's majority opinion in Afroyim v. Rusk (1967), categorically pronouncing the government incapable of terminating an individual's citizenship against her will. Thenceforth the government could undertake termination only where conduct evidenced an intention to relinquish nationality. “In our country, the people are sovereign and the Government cannot sever its relationship to the people by taking away their citizenship” (173). Hence the book's title.

Weil situates the account in a rights frame in which political motive is constrained by judicial agency. An alternative narrative would have the expatriation power waning with the importance of citizenship itself. Witness failed recent efforts to revive expatriation in the post-9/11 era against citizen terrorists; why bother terminating citizenship when (as with Anwar al-Awlaki) a drone offers a more decisive response? But citizenship no doubt continues to count for something, and, as Weil describes, it is now largely insulated from government deprivation. A superb work of legal history, The Sovereign Citizen is a welcome addition to the growing interdisciplinary citizenship literature.