Professor Ernst joined the Georgetown faculty in the 1988-89 academic year. He is the author of Lawyers Against Labor (1995), for which he received the Littleton Griswold Award of the American Historical Association. In 1996, he was a Fulbright Research Scholar at the National Library of New Zealand, and in 1998 he was the Jack and Margaret Sweet Visiting Professor of History at Michigan State University. He teaches courses in American Legal History and Property.