Professor Humbach teaches courses in the law of property, legal ethics, criminal law and the First Amendment. His teaching specialty has been in the property law area for over 30 years.

Prior to entering law teaching in 1971, Professor Humbach practiced corporate and securities law for five years in New York City. Most of his teaching experience before coming to Pace in 1977 was at Fordham Law School, but he also taught at Brooklyn Law School and as a visiting professor at the University of Illinois and the University of Hawaii. He has authored a number of articles in property law areas such as landlord-tenant and the takings clause of the Constitution, as well as computer-assisted instruction programs for first-year law students. His more recent scholarship also includes articles on the First Amendment, legal ethics and the legal profession. Long engaged in conservation and activities, he has been active in the successful effort to achieve permanent protection for Sterling Forest, N.Y. and has served on the boards of directors of the Appalachian Mountain Club and the NY-NJ Trail Conference. Currently he is chairman of his community Architectural Review Board.