In 1856, the U.S. commissioner to China, Peter Parker, declared that the traffic was so “replete with illegalities, immoralities, and revolting and inhuman atrocities,” that its cruelty at times exceeded the “horrors of the ‘middle passage.’” Working conditions at labor sites in the Americas were no better. On the Chincha Islands off the coast of Peru, trafficked Chinese workers mined guano, a fertilizer used on American farms and plantations. They labored up to 20 hours per day in a toxic environment, while bosses applied whippings and attacks by dogs as punishment for insubordination. Suicide at the camps was common. On plantations in South America and the Caribbean, experienced observers reported migrants were “treated as slaves,” sometimes “worse than brutes.”

By the eve of the Civil War, media exposés and government reports had publicized these abuses sufficiently to convince most Americans that the traffic was “only another form of the slave-trade,” which had been banned decades before. In 1862, Congress banned the carriage of “coolies” on American vessels. The act was one of many reforms intended to fundamentally restructure American society around a liberal notion of free labor.

But while intended as a humanitarian act, the law helped solidify white Americans’ prejudice against Chinese migrants of all kinds, who came to be understood as “naturally” servile because they had supposedly “allowed” themselves to be trafficked—a prejudice later deployed to justify the Chinese Exclusion Act of 1882, and subsequently transferred to other Asian migrants. Meanwhile, the trafficking of contract laborers worldwide continued well into the 20th century. The unfree conditions it produced has no shortage of modern analogues—as historians have often noted. In 2016, for instance, the UN warned Qatar to end “migrant worker slavery,” a system in which sponsoring employers wield nearly absolute power.

Common to all of these stories is the subordination of a minority group—usually made up of foreigners and other marginalized people—for the economic and social benefit of the majority, using the tools of political disenfranchisement and the impairment of legal rights. This is what makes the immigration proposal put forward by Posner and Weyl last month so alarming. Their plan aims to cut through the current immigration-policy impasse by giving working-class Americans—presumably, the white ones concerned about “illegal aliens”—a contracted property right in the labor of immigrants. It would “achieve the goals of both sides of the immigration debate,” they write, by allowing immigrants into the country to the economic benefit of those already here.

But their plan seems more likely to produce an effect similar to that achieved when Virginia’s colonial governors interposed whiteness between indentured English servants and enslaved Africans: That is, it would gradually establish an impenetrable social barrier between ordinary American citizens and outcast immigrant workers. Bit by bit, the United States would transform as legislators, judges, and administrators adjudicated countless matters pitting the interests of sponsoring citizens (who could vote) against the interests of immigrants (who could not). The deepening divide would corrode democracy twice over: first, by excluding immigrants from having a political voice and rights, and second, by encouraging a social hierarchy that would inevitably intensify class distinctions among citizens, too.