As a member of the Jeju Special Self-Governing Provincial Council, he served as the chairman of the Special Committee on Budget and Account. Currently, he is a representative member of the "Human Rights, Welfare and Social Policy Forum," a research group of council members. He also serves on the Autonomy Administration Committee, which is in charge of human rights. For more than 30 years, he has been an advocate of human rights movements and social welfare policies. Koh Hyeon–su is known for his drive, optimism and clear thinking in the resolution of issues. In 2015, he led the enactment of the Jeju Special Self-Governing Province Human Rights Guarantee and Promotion Ordinance with human rights organizations in Jeju as a standing representative of Jeju Human Rights Association. For his achievements, he was awarded the Grand Prize in the Excellence Council, the Grand Prize in Universal Design, and the Grand Prize in Welfare Activities for the Disabled in Korea.

고현수는 제주특별자치도의회 의원으로 예산결산특별위원장을 역임하였고 현재 의원연구모임 “인권과 복지사회정책포럼” 대표의원이며 인권 주무위원회인 행정자치위원회에서 활동 중이다. 30여년을 인권운동과 사회복지활동에 복무하였다. 제주인권단체연석회의 상임대표로 있던 2015년, 도내 인권단체와 함께 「제주특별자치도 인권보장 및 증진조례」 제정을 주도하는 등 강한 추진력과 사안해결에 합리성을 겸비하고 있다는 평이다. 그 공적으로 우수의정 대상, 유니버설디자인 대상, 한국장애인복지활동가 대상 등을 수상하였다.