DMZ is as a boundary line of S.korea and N.korea ,therefore, access is strictly controlled in this military areas. TODAY korean and foreign visitors can enter DMZ but only allowed in some special areas.So, DMZ tour and visit of the third tunnel are recognized as essential courses of travel in korea by foreign visiors to korea.
Although koreans are allowed to visit only some special areas since 1987, their access of Panmunjom still needs strict examinations. Foreign travelers , not koreans are went through simple process like submiting passport number.
if you make a reservaion of observatory and the 3rd tunnel 1-2 days prior , you will be able to visit. you need to submit your name, passport number or a copy of passport at least 3-4 days prior. After getting access permission, your tour of Panmunjom can be allowed. it is impossible to visit privately.