Russia is waging a cross-border legal battle at the High Court against William Browder, the former hedge fund manager whose campaign for international sanctions against Russian officials has pitted him against the state for nearly a decade.

Browder managed billions of dollars of investments in Russia until he pulled out of the country more than a decade ago. Born an American citizen, he now carries a British passport and lives in London. In 2012, Browder successfully lobbied US Congress to pass sanctions on Russian human-rights abusers.