Commentary South Korean President Moon Jae-in is coming to Washington and will meet President Joe Biden on May 21. Moon’s term in office ends next year, but he’s got a big objective: to ‘school’ Biden on North Korea and convince him to follow Moon’s own approach to dealing with Pyongyang and its dictator Kim Jong Un. Moon’s approach: hold talks with North Korea and offer ‘sanctions relief.’ Moon says he is confident Kim will make concessions, and via a ‘mutually trusted roadmap’—Kim will eventually give up his nuclear weapons, and there will be peace on the Korean peninsula. One doubts, however, that Moon has ever seen a copy of the mutually trusted road map. Since taking office in 2017, Moon has been trying out the policy he plans to sell to Biden. The results: North Korea still has nuclear weapons and long-range missiles to deliver them. And the arsenal is …