1392- 1910 Choson Korea
King T’aejo unified Korea. He & his dynasty adapted the Chinese model of statutes (administrative rules) and criminal code. Confucian, Neo-Confucian (late 14th century) and Buddhist philosophy were underlying influences.
1910 - 1940s Colonial rule by Japan
Japan's rule brought with it the influence of the German tradition of Roman law.
The WW2 Allies had agreed that their victory should lead to the return of independence to Korea. The path to achieve this has meant the destiny of Korea became a problem & a challenge for the new international legal system and the newly formed United Nations.
By the time Japanese occupation ended, Soviet troops occupied north of the 38th parallel, while the USA administered the area to the south. So the Korean peninsula was a flash point of cold war tensions, especially after 1950, when South Korea declared independence, & the North responded militarily.
The UN called upon member states to provide aid to South Korea: 45 member states responded in a variety of ways - some militarily. This meant the People's Republic of China felt threatened and sent in troops too.
See article on Korean War in MPEPIL via link below.
1953 Direct military hostilities end with an armistice, no peace treaty. The peninsula remained divided geographically, with discrepancies in ideologies & political systems & aspirations across the border.
1991 both Koreas were admitted as members of UN
1999 North/South tensions flare over exact configuration of the maritime boundary in the West (or Yellow) Sea
2006 North Korea tests its first nuclear device