Haines earned his B.A. at St. Olaf College in 1961, his J.D. at the University of Montana Law School in 1964, and an LL.M. in Taxation from New York University Law School in 1966. Following his 1964 admitted to the Montana Bar and U.S. District Court, Montana, he practiced law in Missoula, Montana, as a partner in the law firm of Worden, Thane & Haines from 1966 to 2003, also serving as an adjunct professor in the University of Montana Law School from 1967-1991. Haines was appointed by President George W. Bush as Judge, United States Tax Court, on April 22, 2003 for a term ending April 21, 2018.