Marc represents businesses and trade groups before US federal and state agencies, the US Congress, and foreign governments on a broad range of regulatory, administrative, and legislative matters. He also represents clients in maritime and commercial litigation and arbitration matters. Marc has published numerous articles on international trade, maritime, and environmental law, and has written and spoken at dozens of seminars and conferences focused on these topics.

Throughout his career, Marc has been active and held leadership roles in a variety of professional associations, including serving as chair of the Greater New Orleans Port Safety Council (2011, 2016, 2017, and 2018) and co-moderator and member of the Seminar Steering Committee for the Greater New Orleans Barge Fleeting Association, River and Marine Industry Seminar (2013 to present). In 2008, he was appointed by US Commerce Secretary Carlos Gutierrez and the United States Trade Representative (USTR) Ambassador Susan Schwab to serve on the Industry Trade Advisory Committee 14, where he served until 2010.

Marc practiced law with Bracewell & Patterson in Washington, DC, from 1996 to 2002. Before that, he worked for the US House of Representatives Government Reform and Oversight Subcommittee on National Economic Growth, Natural Resources, and Regulatory Affairs. From 2002 to 2005, he was an adjunct professor at the Loyola University New Orleans College of Law.