From 1936 to 1949, he served as a special assistant in the Antitrust Division of the United States Department of Justice.

He assumed senior status on December 31, 1976, serving in that capacity until his death on September 6, 1997, in Uniontown.

[2] In addition to his legal and judicial duties, Dumbauld wrote extensively for scholars and general readers about the life and work of Thomas Jefferson, the United States Declaration of Independence, and the United States Constitution and United States Bill of Rights, as well as the Renaissance legal philosopher and treatise-writer Hugo Grotius.

[citation needed] He was a longtime member of the American Society for Legal History.

[citation needed] His books, many of them standards of American legal-historical literature, include: