Gustavo Petro: Colombia’s former rebel fighter turned president

In 2007, Gustavo Petro was visiting Washington, DC, when he made an unusual request: to accompany his host’s friend on a school pickup run.

At the time, Petro was a rising star in the Colombian Senate who was in the United States to receive the Letelier-Moffitt Human Rights Award for exposing politicians’ ties to paramilitary groups. His host was Sanho Tree, director of drug policy at the Instit...