After practicing law in Salt Lake City, Utah for four years, he became an assistant to BYU president
Dallin H. Oaks. He was on the original faculty of BYU's
J. Reuben Clark Law School (JRCLS), founded in 1973. His teaching and research focused on constitutional, education, and family law—particularly the legal rights of children. His professional scholarship was published in such journals as the
Harvard Law Review,
Harvard International Law Journal,
Michigan Law Review,
Duke Law Journal,
Brigham Young University Law Review,
Ohio State Law Journal, and the
American Bar Association Journal. Two of his articles were cited in opinions of the
U.S. Supreme Court. One of his central insights about children's rights was that the legal system “limits children’s [legal] autonomy in the short run in order to maximize their development of actual autonomy in the long run. . . . [To] short-circuit this process by legally granting [autonomy]—rather than actually teaching autonomous capacity--to children ignores the realities of education and child development to the point of abandoning children to a mere illusion of real autonomy." From 1976 to 1978, Hafen was the director of evaluation and research for the LDS Church's Correlation Department. He then served as president of
Ricks College (now
Brigham Young University-Idaho) from 1978 to 1985. At the time Hafen took the helm at Ricks it had an enrollment of 6,000 students. During this time, he was also president of the American Association of Presidents of Independent Colleges and Universities (AAPICU) and a Commissioner on the Northwest Commission on Colleges and Universities—the regional accrediting authority for higher education institutions in the seven Northwestern states. While president of Ricks, Hafen taught at least one class each semester. Hafen was Dean of the JRCLS from 1985 to 1989. While there he helped to create an international
law society for LDS Church members and others who were lawyers. By 2017, the law society had over 10,000 members in more than 100 chapters, a third of them outside the U.S. Hafen also raised donated funds to establish a series of endowed professorships to support law faculty scholarship. The JRCLS later created an endowed professorship and an endowed annual lectureship in Hafen's name. From 1989 to 1996, he was the
provost at BYU. As provost, he worked with the faculty to develop a policy that appropriately blended BYU's institutional academic freedom as a religious university with the faculty's individual academic freedom, along with a new policy statement describing “The Aims of a BYU Education.” == LDS Church service ==