Widely recognized as a foremost expert in copyright law, David Nimmer represents clients in the entertainment, publishing and high technology fields. He has twice served as co-counsel representing clients before the U.S. Supreme Court. On the first occasion, a unanimous decision in favor of his client drew the boundaries between copyright and trademark protection. In the second, another unanimous decision in favor of his client set the stage to compensate all freelance journalists in the country for their past articles.

David gave congressional testimony at the invitation of the House Judiciary Committee in 2014, on behalf of the United States Telephone Association in 1997 and on behalf of the National Association of Broadcasters in 1992. He also delivered Parliamentary testimony on behalf of the Combined Newspaper and Magazine Copyright Committee of Australia in Sydney.

Since 1985, David has authored and updated Nimmer on Copyright, the standard reference treatise in the field, first published in 1963 by his late father, Professor Melville B. Nimmer. The U.S. Supreme Court has cited Nimmer on Copyright on numerous occasions, as has every federal appellate court, countless district and state courts, as well as courts confronting copyright cases in countries across the globe. Cases within the United States have relied on Nimmer on Copyright as authority in over 3,500 judicial opinions.