BOGOTA, Colombia (AP) — After negotiating the demobilization of the M-19 rebel movement he co-led, Antonio Navarro helped draft Colombia’s 1991 constitution, ran for president and became a big-city mayor and a state governor. And he did it all bearing the scars of war: a wooden leg and slurred speech from a grenade attack.

If anyone understands the bitter costs and frustrating political complexities of Colombia’s half-century-old conflict, it is Navarro. That’s why, he says, he is backing President Juan Manuel Santos’ “Peace Framework” law, a constitutional amendment that sets a roadmap for government negotiations with leftist rebels.