Mark is the Chair of the Firm's Labor Practice Group.  He is also the Chair of the West Virginia Chamber of Commerce Human Resources Committee and member of the Labor Relations Committee of the United States Chamber of Commerce.

He has advised and represented employers throughout the United States in corporate campaigns, collective bargaining, arbitrations, and federal litigation involving labor unions as well as serving employers in employment litigation. He has litigated in Alaska, New Jersey, Idaho, Michigan, Alabama, and other states and has advised clients in Washington state, Puerto Rico, California, New York, Florida, the District of Columbia, and the majority of the states in the nation.

Mark has testified before the United States Senate and the House of Representatives. He is a former management chair of the Antitrust RICO and Labor Law Committee of the American Bar Association and has spoken at more than 10 annual meetings of that organization. He has also spoken for the U.S. Chamber of Commerce, the Canadian Association of Counsel to Employers, the Labor Policy Association and other national trade groups.

He previously served as the chairman of the Federal Service Impasses Panel upon the appointment of President Trump in July 2017. He and his colleagues resolved impasses in collective bargaining between the United States Government and unions representing federal employees. From 2002 through 2009, he served as a member of the Federal Service Impasses Panel upon three successive appointments by President George W. Bush.