Prior to entering teaching, he practiced law in Washington, DC and Austin, Texas for 12 years, working on numerous land use and environmental law issues for industry, land development projects, and local governments. In addition to Vanderbilt, where he joined the law faculty in July 2011, Professor Ruhl has taught at Florida State University (1999-2011), Harvard Law School (visiting spring 2008), Vermont Law School (summers 2001 and 2014), George Washington University (visiting 1998-99), Southern Illinois University (1994-1998), University of Texas (summer 1997), and Lewis & Clark (summer 1996).

He has written over 40 scholarly articles in the field, made numerous presentations to academic and professional groups, and is co-author of two law school casebooks, The Practice and Policy of Environmental Law (Foundation Press 3d ed. 2014) and The Law of Biodiversity and Ecosystem Management (Foundation Press 3d ed. 2013). He has served in the past as an Officer of the American Bar Association Section on the Environment, Energy, and Resources, and as the Editor-in-Chief of the Section's quarterly legal journal, Natural Resources & Environment.