From The Twilight of Human Rights Law, by Eric A. Posner, out next month from Oxford University Press. Posner is a professor at the University of Chicago Law School.

Amarildo de Souza, a bricklayer living in a favela in Rio de Janeiro, was arrested by police in 2013 as part of an operation to round up drug traffickers. He was never seen again. De Souza’s disappearance was taken up by protesters in street demonstrations, which in turn were also met with a ruthless police response. Normally, de Souza’s story would have ended there, but public pressure led to a…