Ireland's Prime Minister described the result as the culmination of a "quiet revolution" in what was once one of Europe's most socially conservative countries.
The two leaders met at the demilitarized zone on the Korean border.
Bans on plastic straws are starting to catch on. But a similar fight against plastic bags shows just how hard it is to regulate plastics.
The man's release comes a little over a week after he posted two short videos on his Facebook page in which he said a prison riot was endangering his life.
"Some Western observers have been happy to turn a blind eye," said Jane Kinninmont, deputy head of the Middle East and North Africa program at Chatham House, a London think tank.