This paper deals with how to understand the Korean adult guardianship law from the perspective of persons with severe mental health problems. Because adult guardianship law can be traced back to the Roman law in 5th century BC, which aimed to exclude persons with mental health problems, the focus should be on the development of mental health policies in western countries, which have, in turn, influenced Korean policy as well, to correctly understand the current Korean adult guardianship law. Briefly mentioning the development of mental health policies, this paper argues that the right to self determination, including support for it, is the main purpose of guardianship law reform in western countries. This paper suggests that Korean guardianship law, which still contains many elements of old-fashioned guardianship law, should be read and implemented in the light of respecting the right to self determination and that involuntary admission of persons with severe mental illness to psychiatric hospitals, institutions and nursing homes and de-facto involuntary treatment of them, the most controversial issue of the negations of the right to self determination, should be re-interpreted as well.