Terry N. Trieweiler graduated from Drake University School of Law in 1973 and was admitted to practice in Montana in 1975. He was certified as a specialist in civil trial advocacy by the National Board of Trial Advocates in 1982; elected president of the Montana Trial Lawyers Association in 1984; and elected president of the State Bar of Montana in 1986.
He was included in the directory of the "Best Lawyers of America" in 1987 and 1989. During 1989 he also served on the Board of Directors for the Association of Trial Lawyers of America, and was a member of the Board of Directors of the American Board of Trial Advocates.
He has been a member of the International Society of Barristers since 1985, and taught Civil Procedure at the University of Montana School of Law prior to being elected a Justice on the Supreme Court of Montana where he served from 1991 to 2003.