Datuk Mairin Bin Idang @Martin was admitted as an Advocate of the High Court in Borneo (now Sabah and Sarawak) on the 23rd February 1982. He served as a legal assistant at Messrs Yap & Chin, Advocates & Solicitors of Kota Kinabalu from July 1985 to February 1986. In March 1986 until December 1987, he was a legal assistant in Messrs Le & Thong, Advocates & Solicitors of Kota Kinabalu. He commenced practice as Messrs Idang & Co. on the 2nd February 1988 (as a sole legal practitioner). In 1991, the firm of Messrs Richard Malanjum & Co., Messrs Idang & Co. and Messrs D T Rantau & Co. merged as consortium under the name of Messrs Richard Malanjum Idang & Rantau. In 1993, due ot the elevation of Tun Richard Malanjum as High Court Judge, the firm's name was changed to Messrs Martin Idang Rantau & Co. He remained as a partner in the firm until his appointment as a Judicial Commissioner in the High Court of Sabah & Sarawak on the 12th November 2013. He then was elevated as a High Court Judge in 2018 until he retired on the 21st November 2020. In 2022, he resumes practice as an Advocate & Solicitors in Sabah under the name of Messrs MIRAM & Co until now.