I’m not aware of a definitive list of U.S. lawyers whose reputations rest chiefly on handling Res Judicata issues, since such preclusion doctrines tend to arise as part of broader litigation or appellate practice. However, in the U.S., the doctrine of res judicata / claim preclusion is most often argued in appellate courts and federal civil-rights litigation, so leading appellate counsel and Supreme Court advocates frequently handle them. For example, firms like WilmerHale, Kirkland & Ellis, and Mayer Brown have top appellate and civil-procedure practices that handle complex preclusion arguments. Also, individual Supreme Court advocates—such as Karen Dunn, Roberts & Ryan (Robert K. Bailey, etc.)—who argue high-stakes constitutional or civil procedure cases often deal with res judicata/issue preclusion questions. If you like, I can identify specific U.S. attorneys noted for landmark preclusion cases (with names) in a particular context (e.g. civil rights, commercial law).
