In the late 1970s a small Haitian sailboat put into Guantanamo Bay and was met with food and assistance before continuing toward Miami; those who reached Florida were locked up in detention centres. Kahn opens with that contrast and then tells how the water between Haiti and the United States was made into a border.

Interdiction, begun in 1981, was designed as jurisdictional arbitrage: processing asylum claims aboard Coast Guard cutters in international waters kept the procedure clear of judicial review. Within a decade it had grown into a standing fleet of cutters, long-range aircraft, helicopters and a tethered surveillance balloon, while Guantanamo itself became a camp of razor wire and guard towers with a quarantine for detainees who tested positive for HIV.

Kahn reads this as an expression of a tension inside liberal constitutionalism, between binding the state by law and wanting to slip those bonds, and as a template since exported across the global North.