In May 2007 Jeff Gewirtz began his tenure as Senior Vice President and General Counsel for the NBA's New Jersey NETS and in December 2010 was promoted to Executive Vice President and Chief Legal Officer. In addition to oversight of all legal affairs for the franchise, Gewirtz serves in the same role for BROOKLYN SPORTS & ENTERTAINMENT (BSE), a NETS' affiliate that is handling all commercial and sports marketing aspects of the NETS' planned 2012 relocation to the Barclays Center in downtown Brooklyn, New York, as well as the booking of all other sports and entertainment content for the Barclays Center, including major college sports, concerts, family entertainment, and special events.  BSE also represents properties and venues in the negotiation of naming rights transactions such as the IZOD CENTER. Through BSE, Gewirtz has also consulted the Beijing Organising Committee for the 2008 Olympic Games on its wind-up and dissolution process.

In March 2009 Gewirtz was named as a Sports Business Journal FORTY UNDER 40.

Gewirtz formerly served as the United States Olympic Committee General Counsel and Chief Legal & Government Affairs Officer. While there he oversaw all USOC legal matters, including areas such as litigation and arbitration, intellectual property matters, athlete and sport national governing body matters under the Ted Stevens Olympic and Amateur Sports Act, anti-doping, real estate, and sponsorship, media, and licensing transactions. Gewirtz also had oversight of the USOC's government relations activities with Congress and Federal government agencies and he served as counsel to the USOC's 2016 Olympic Games Domestic Bid City Evaluation Commission.

Prior to joining the USOC Gewirtz was Counsel — sports & entertainment transactions, marketing and media in The Coca-Cola Company's Corporate Legal Division. His primary responsibilities at Coca-Cola included the provision of legal counsel on and the structuring and negotiation of the Company's North American sports marketing and media transactions with professional sports leagues, team, stadiums, arenas, and professional athletes. In that role, Gewirtz served as lead counsel for Coca-Cola North America's two largest sports industry transactions: (i) its over $500 million sponsorship and media alliance with CBS Sports, designating Coca-Cola as an NCAA Corporate Champion and granting Coca-Cola marketing rights across all 88 NCAA Championships; and (ii) its $170 million naming rights transaction with the Houston Astros for the naming of Minute Maid Park. In the winter and spring of 2005, Gewirtz served as counsel to Coca-Cola's eight-country Southeast and West Asia Division, based out of Coca-Cola's division office in Bangkok, Thailand.

Prior to joining Coca-Cola, Gewirtz was Director of Legal Affairs for IOC Television & Marketing Services SA, based in Lausanne, Switzerland. In that role he served as the legal point person and primary negotiator of the International Olympic Committee's global sponsorship alliances under The Olympic Partners (TOP) Program with companies such as Coca-Cola, Eastman Kodak, John Hancock, McDonald's Corporation, Samsung Electronics, Swatch/Omega, and VISA. Gewirtz also negotiated global sponsorships and technology license agreements on behalf of the 2002 Salt Lake Olympic Organizing Committee and the 2004 Athens Olympic Organising Committee. Prior to his IOC work, Gewirtz was General Counsel of the LPGA Tour. He has also worked in-house in the legal and business affairs department of the WTA Tour and began his legal career as an associate attorney with the New York City law firm of Dunnington, Bartholow and Miller, LLP, where he served as associate to the United States Tennis Association's General Counsel and worked in the Firm’s Corporate and Advertising Industry Practice Groups.  From 1997 through 2002 Gewirtz also held the pro bono position of General Counsel to USTA/Eastern, Inc., the Eastern Section of the United States Tennis Association.

In addition, Gewirtz was formerly on the faculty of Brooklyn Law School and New York Law School, serving as an adjunct professor of sports law at both schools.  He is currently Chair of the Sports Division within the American Bar Association's Forum on the Entertainment and Sports Industries and he sits on the Board of Directors of the National Sports Law Institute and on the Advisory Board of the Penn State Institute for Sports Law, Policy, and Research. He was also recently appointed to the Board of Editors of the Journal of International Media & Entertainment Law. In 2003, Gewirtz was named by the Fulton County Daily Report to its annual "Lawyers on the Rise" list under the age of 40 in the state of Georgia. He has also lectured extensively, both in the United States and internationally, on a variety of sports industry legal and business issues, including before groups such as the African National Olympic Committees, the Oceanic National Olympic Committees, the Australia-New Zealand Sports Lawyers Association, and at the 2002 SportAccord Conference in Madrid, Spain.

Through his seat on the Sports Lawyers Association (SLA) Board of Directors, Gewirtz served as Chair of the 2011 SLA Conference in Washington, DC and he also serves as Chair of the SLA's Sponsorship Committee of the Board.

Gewirtz is a graduate of Tufts University, where he was a four-year member and 1990-91 captain of the Tufts Varsity Tennis Team and a member of Tufts' 1989 New England Championship team. Gewirtz also qualified to compete on the United States Team, in the men's tennis competition, for the 17th World Maccabiah Games held in Tel Aviv, Israel in July 2005. He received his law degree from Brooklyn Law School, where he was the recipient of a three-year merit scholarship.

As a junior tennis player, Gewirtz held the number 1 doubles ranking in the Eastern Tennis Association (ETA) and the number 1 singles ranking for the Long Island District of the ETA.