On May 21, 2009, the Supreme Court of Korea ruled that patients have the right to terminate medically meaningless treatment upon confirmation that their terminal illness is indeed irreversible. The Supreme Court`s decision thus makes proof of the irreversibility of a patient`s condition an important process in legitimatizing a patient`s decision to terminate life-sustaining treatment. However, since medical practice rejects explanations in terms of "essences" and is affected by issues of subjectivity, we argue that physicians cannot give indisputable confirmation of the irreversibility of a patient`s terminal illness, as required by the Supreme Court`s ruling.