Maurice “Hank” Greenberg, the former chairman of American International Group, has reached a dead end in his company’s $25 billion lawsuit alleging that the Federal Reserve Bank of New York’s takeover of AIG was unlawful.

In a nine-page decision issued on Wednesday, the U.S. Court of Appeals for the Second Circuit dismissed Greenberg’s claims that FRBNY breached fiduciary duties to AIG shareholders under Delaware law. Affirming U.S. District Judge Paul Engelmayer in Manhattan, the appeals court wrote that Greenberg’s breach of fiduciary duty claims are preempted by federal law.