Biography
Zack joined Weil from the U.S. Department of Justice, where he served for five years as an Assistant to the U.S. Solicitor General. In that role, he represented the United States in litigation in the Supreme Court, and assisted in coordinating the government’s appellate strategy in lower courts nationwide. Zack previously served as Special Counsel to the General Counsel of the U.S. Department of Defense and Attorney Adviser at the U.S. Department of State.
Zack is recognized by Chambers USA as a leading lawyer nationally for Appellate Law, with commentators touting that he is “absolutely, positively, incredibly talented…he’s an appellate generalist who can do anything very well,” “an excellent appellate lawyer,” and calling him “...very good at managing a case and keeping everything moving smoothly. If you have a complex brief or argument to run, he’s the guy to go for. You want him on your side.” He also is ranked as a “Leading Lawyer” by Legal 500 for both Appellate: Courts of Appeal and Appellate: Supreme Courts, where clients note that he is “phenomenal,” “extremely quick-thinking,” and “knows the U.S. Supreme Court especially well.” Additionally, Lawdragon 500 selected him to its 2025 “Leading Litigators in America” list and to its list of “500 Leading Lawyers in America.”
Some of Zack’s notable engagements include:
- Securing a unanimous win in the Supreme Court in Bartenwerfer v. Buckley, which held that the fraud exception to discharge under the Bankruptcy Code applies to a debtor’s liability for the actual fraud of a business partner, when the debtor did not personally perpetrate the fraud but is vicariously liable for it under state law.
- Representing a tech company in several appeals involving the application of Section 230 of the Communications Decency Act to cryptocurrency and internet gambling apps.
- Representing a major cryptocurrency and blockchain technology company in SEC enforcement litigation.
- Advising companies on litigation and business risks stemming from the deployment of generative AI.
- Representing GrubHub in an interlocutory appeal involving arbitrability of claims in an antitrust class action.
- Representing CareDx in a series of appeals in involving cutting-edge biotechnology patents.
- Representing Zion Williamson in a dispute between the 2019 NBA #1 draft pick and his former agent, who has asserted claims of more than $100M in damages. Zack helped Williamson obtain a complete win at the trial court and on appeal before the Fourth Circuit.
- Representing the U.S. Chamber of Commerce as amicus curiae in a series of U.S. Supreme Court cases regarding the scope of the Federal Arbitration Act.
- Representing Bridgestone in a significant victory in the Sixth Circuit regarding the scope and preclusive effect of a prior settlement with a nationwide class action of indirect purchasers.
- Representing Westinghouse Electric Company in a successful certified interlocutory appeal before the Third Circuit that addressed whether a bankruptcy court can discharge and bar administrative claims that arose after confirmation of a plan, but before the plan became effective.
- Representing Upsolve, Inc. in the Southern District of New York in obtaining a landmark win in a First Amendment challenge to protect Upsolve’s mission to train non-lawyers to provide limited legal advice to low-income New Yorkers who face debt collection actions.
- Representing the United States Men’s National Soccer Team in landmark litigation supporting equal pay for the United States Women’s National Soccer Team.
- Representing several Rastafarian former inmates in appeals seeking to obtain money damages under the Religious Land Use and Institutionalized Persons Act, when prison officials violated their religious rights by forcibly cutting their dreadlocks.
- Before joining Weil, Zack argued and won important Supreme Court cases on subjects including bankruptcy law (Mission Product Holdings v. Tempnology), patent law (Life Technologies Corp. v. Promega Corp. and WesternGeco v. ION Geophysical Corp.), insurance (Coventry Health Care of Missouri v. Nevils), and administrative exhaustion (Ross v. Blake).
Zack received his B.A., cum laude, from Yale University and his J.D. from Columbia Law School, where he was a James Kent scholar and served as an Articles Editor of the Columbia Law Review. After graduating, Zack clerked for Judge Amalya Lyle Kearse of the U.S. Court of Appeals for the Second Circuit, and for Justice Ruth Bader Ginsburg of the U.S. Supreme Court.