After earning his undergraduate degree in history and economics, Tom Nachbar spent five years as a systems analyst, working for both Andersen Consulting and Hughes Space and Communications before entering law school, where he served on the University of Chicago Law Review and was elected to the Order of the Coif. After graduation, he clerked for Judge Frank H. Easterbrook of the U.S. Court of Appeals for the Seventh Circuit and later practiced with what is now Mayer Brown in Chicago as a member of the firm's appellate litigation, information technology, and intellectual property practice groups. Nachbar's previous research has addressed how the availability of new technologies alters conceptions of regulation; his current work is on the relationship between public and private regulation of markets. Nachbar has written extensively on the history of trade regulation, from mercantilist England through 20th-century America, with an emphasis on the constitutional dimensions of trade regulation. He has also written on the relationship between technology and regulation, and has both practiced and published in the field of telecommunications law. He is a co-author (with Glen Robinson) of the casebook Communications Regulation.

In addition to his work on regulation, Nachbar works extensively in the national security arena, focusing on law of armed conflict and the role of legal institutions in counterinsurgency and stability operations. He is a judge advocate in the U.S. Army Reserve, where he has, among other assignments, edited an Army handbook on the development of legal systems, trained Palestinian security forces in the West Bank and deployed to Iraq. He is a senior fellow at the Center for National Security Law.