I studied under Karin Sheldon in law school. She's currently a board member, a former president, and former Chief Litigaiton Counsel for Defenders. She's about as anti hunting as you can imagine (she taught my endangered species law class). If you look at their board of directors, and litigation committee, its a whos who of the looney left.
Eric R. Glitzenstein, of Meyer Glitzenstein & Crystal, serves as HSUS's primary outside counsel.