A Massachusetts judge on Wednesday dealt state securities regulators a major setback in their enforcement action against the online brokerage Robinhood by declaring the state's new fiduciary rule which underlies the case invalid.

Suffolk County Superior Court Judge Michael Ricciuti in Boston concluded that Massachusetts Secretary of State Bill Galvin's lacked the authority to adopt a rule in 2020 that raised the investment-advice standard for brokers. (Reporting by Nate Raymond in Boston)