Jonathan represents clients in complex and high-stakes disputes, including appeals, transnational litigation, False Claims Act matters, and disputes over art and artifacts.

He handles appeals in the U.S. Supreme Court, every federal circuit, and state appellate courts nationwide. He has successfully vindicated clients’ most important intellectual property interests on appeal, including defeating a Nobel Prize winner in litigation over the ownership of the patent on the Nobel-winning technology. His victories in major commercial matters include reversals in a nine-figure case in the U.S. Supreme Court and in eight-figure cases in the Supreme Courts of California, Georgia, and Connecticut, where he reversed what was then the largest class-action or commercial judgment ever issued in the state. And he has preserved important judgments for clients, including setting a record for the largest judgment ever affirmed by the Connecticut Appellate Court, and preserving, on alternative grounds, an important patent ruling in the Federal Circuit in a long-running transnational dispute.

Jonathan counsels clients in disputes involving art and artifacts, including claims involving provenance, authenticity, and export law. He has successfully defended a client’s title to one of Van Gogh’s most famous paintings, garnered a U.S. Supreme Court victory for Germany and the Berlin equivalent of the Smithsonian in a case alleging that a major collection of medieval art was obtained through duress in the Nazi era, and represented Yale University in its litigation with Peru over Incan artifacts from Machu Picchu. He regularly counsels clients on the investigation and resolution of claims involving provenance, cultural property, and authenticity, and he assists museums outside the U.S. in understanding, defending and resolving claims involving U.S. law. Jonathan has taught Art and Artifacts Law at Yale Law School, where he was the first practicing lawyer to teach art law, and he is listed in the Chambers High Net Worth guide as one of the leading lawyers in the U.S. in Art and Cultural Property Law. The U.S. Copyright Office has cited him in a report to Congress on copyright in the visual arts.

He represents sovereign nations and foreign sovereign officials in pursuing or defending claims in the United States. He has vindicated a former president of Mexico wrongly accused of violations of international human rights law, represented a foreign sovereign nation claiming RICO violations against a U.S. company, and has represented foreign sovereigns on Foreign Sovereign Immunities Act issues. He has represented foreign ambassadors and former senior U.S. officials.

Jonathan has deep experience litigating international disputes in U.S. courts and frequently works with counsel in other nations, whether on coordinated multinational litigation or by advising on U.S. law. His assistance to counsel in other nations includes providing expert testimony on U.S. law in foreign judicial proceedings.  

Among other recognitions, Chambers USA ranks Jonathan in its highest band, noting that clients have described him as “absolutely brilliant,” “a fiercely bright appellate lawyer who handles high end problems,” “a very cost-effective resource in contentious matters,” and “probably the very best appellate advocate I have ever seen.” Legal 500’s appellate rankings have reported clients describing Jonathan as “extraordinarily bright and practical…a rare combination and one that provides tremendous value to his clients,” “an exceptional advocate,” “absolutely outstanding,” “knowledgeable, erudite, incredibly articulate and strategically excellent.” He is an elected Fellow of the American Academy of Appellate Lawyers.