Known as Duch, he ran the regime’s most notorious prison and oversaw the torture and killings of as many as 16,000 Cambodians.
Nuon Chea and Khieu Samphan were sentenced to life in prison.
"Every country has a right to protect their country, but think about our past."
These men have served their sentences and were leading otherwise regular lives with spouses, children, and jobs when they were detained.
A U.N. envoy said the decision sent a message to leaders in North Korea and elsewhere.