In GP and others (South Korean citizenship) North Korea CG  UKUT 391 (IAC) the tribunal concludes, to cut a long story short, that North Koreans can jolly well go back to South Korea whether they like it or not. Henceforth. Whereforeunto. Hereafter. Thereof.
The official headnote:
(1) The Upper Tribunal’s country guidance in KK and others (Nationality: North Korea) Korea CG  UKUT 92 (IAC) stands, with the exception of paragraphs 2(d) and 2(e) thereof. Paragraphs (2), (3) and (4) of this guidance replace that given in paragraphs 2(d) and 2(e) respectively of KK.
(2) South Korean law makes limited provision for dual nationality under the Overseas Koreans Act and the Nationality Act (as amended).
(3) All North Korean citizens are also citizens of South Korea. While absence from the Korean Peninsula for more than 10 years may entail fuller enquiries as to whether a person has acquired another nationality or right of residence before a travel document is issued, upon return to South Korea all persons from the Korean Peninsula are treated as returning South Korean citizens.
(4) There is no evidence that North Koreans returned to South Korea are sent back to North Korea or anywhere else, even if they fail the ‘protection’ procedure, and however long they have been outside the Korean Peninsula.
(5) The process of returning North Koreans to South Korea is now set out in the United Kingdom-South Korea Readmission Agreement (the Readmission Agreement) entered into between the two countries on 10 December 2011. At present, the issue of emergency travel documents under the Readmission Agreement is confined to those for whom documents and/or fingerprint evidence establish that they are already known to South Korea as citizens, or who have registered as such with the South Korean Embassy in the United Kingdom.
(6) Applying MA (Ethiopia) v Secretary of State for the Home Department  EWCA Civ 289, North Koreans outside the Korean Peninsula who object to return to South Korea must cooperate with the United Kingdom authorities in seeking to establish whether they can avail themselves of the protection of another country, in particular South Korea. Unless they can demonstrate that in all of the countries where they are entitled to citizenship they have a well-founded fear of persecution for a Refugee Convention reason, they are not refugees.
(7) If they are not refugees, it remains open to such persons to seek to establish individual factors creating a risk for them in South Korea which would engage the United Kingdom’s international obligations under the EU Qualification Directive or the ECHR.
(8) There is no risk of refoulement of any North Korean to North Korea from South Korea, whether directly or via China. South Korea does not return anyone to North Korea at all and it does not return North Koreans to China. In a small number of cases, Chinese nationals have been returned to China. A small number of persons identified by the South Korean authorities as North Korean intelligence agents have been prosecuted in South Korea. There is no evidence that they were subsequently required to leave South Korea.
(9) Once the ‘protection’ procedure has been completed, North Korean migrants have the same rights as other South Korean citizens save that they are not required to perform military service for South Korea. They have access to resettlement assistance, including housing, training and financial assistance. Former North Koreans may have difficulty in adjusting to South Korea and there may be some discrimination in social integration, employment and housing, but not at a level which requires international protection.