One evening in March, almost exactly seven years ago, Steven Thomas of Irell & Manella went to dinner at Hotel Bel-Air, a Los Angeles hotel that bills itself as the place “where the rich and famous go to hide.”

Thomas, head of Irell’s art law practice, was with the top executives of one of the world’s most famous auction houses and his client, Maria Altmann. The topic of conversation was five paintings by Gustav Klimt that Altmann and four of her relatives had just inherited after an eight-year legal battle with the Republic of Austria.