Organizers of the event put the blame for the cancellation on the increasing difficulty of travelling between the two countries.
According to numerous published reports, airlines have been reducing the number of flights thanks to a flare up in Chinese/South Korean relations due to the implementation of an advanced missile interception system by American forces in the region.
Word of the cancellation came from an announcement on the WPT website reading:
Due to factors beyond our control, the World Poker Tour (WPT) today announced the cancellation of WPT National Korea scheduled for March 17-21, 2017, at Paradise Casino at Jeju Grand.
As you may be aware, several major airline carriers have suspended air travel in the region. In the best interest of our players, the event will no longer be taking place.
Diplomacy and international politics rarely have this big an impact on World Poker Tour Events, but the WPT stop at the island resort of Jeju is something of a special case. According to a report on FlushDraw.net, about half the players expected to participate in the event are Chinese. This makes sense given the fact that 85 percent of Jeju visitors are Chinese nationals.
This is, apparently, the first time that international politics have led to the cancellation of a World Poker Tour Event.
So far, the event has not been rescheduled.