Bogota, Colombia — One of Colombia’s legendary drug lords and a key operator of the Medellin cartel has been deported back to the South American country, after serving 25 years of a 30-year prison sentence in the United States. A short while later, Fabio Ochoa was again a free man.

Fabio Ochoa arrived in Bogota’s El Dorado airport on a deportation flight on Monday, wearing a grey sweatshirt and carrying his personal belongings in a plastic bag. After stepping out of the plane, the former cartel boss was met by immigration officials ...