Frederick Oberlander, a New York lawyer who is fighting federal prosecutors over a long-running criminal contempt investigation related to his threats to expose businessman Felix Sater’s cooperation with the government, succeeded Wednesday in getting government subpoenas voided before the U.S. Court of Appeals for the Second Circuit.

A three-judge panel of the Manhattan-based federal appeals court ruled that the subpoenas, which date back to 2017, were unenforceable because they had not been issued by sitting grand juries, and a district court judge had lacked the ability to enforce a later, validly issued subpoena after a grand jury’s term had expired.