Throughout his 33-year career in private practice, Sack specialized in press law and represented numerous United States and foreign-based media companies.

[6][7][4] Sack was nominated by President Bill Clinton on November 6, 1997, to a seat on the United States Court of Appeals for the Second Circuit vacated by Judge Roger J.

2021): Sack, writing for the panel, held that defendants Trump Corporation, Donald J. Trump, and members of his family were not entitled to have the district court enforce an arbitration agreement in a suit for unfair business practices and deceptive statements regarding a multi-level marketing company.

2011): Sack, writing for the panel, concluded that the tort of hot news misappropriation was preempted by the Copyright Act as applied to the facts of the instant case, which concerned a novel lawsuit by various investment banks, which publish and disseminate equity research reports, against a small Internet-based aggregator of stock tips which sold the investment banks' recommendations to its own clients.

2009): Sack, dissenting in part from the majority opinion en banc, wrote that a Bivens remedy should have been available to a dual Canadian-Syrian citizen who was detained by federal officials at John F. Kennedy airport, repeatedly denied access to a lawyer, and subsequently removed to Syria to be interrogated under torture by Syrian authorities for ten months.

2006): Sack, writing for the panel, affirmed the district court's decision that artist Jeff Koons was protected by the doctrine of fair use, and therefore not liable for copyright infringement, when he incorporated a photographer's copyrighted photo of a woman's feet and lower legs into a larger collage painting, even though Koons had benefited commercially from the work.