Sidley Austin is stuck facing a proposed class action accusing it, along with fellow law firm Tonkon Torp and a set of accounting firms and banks, of contributing to an alleged securities fraud by now-defunct investment fund Aequitas Management LLC.

U.S. District Judge Michael Mosman in Portland, Oregon, has shot down most of a motion to dismiss the suit, brought by Aequitas investors against law firms Sidley and Tonkon Torp; auditors EisnerAmper LLP and Deloitte & Touche LLP; and banks TD Ameritrade Inc. and Integrity Bank & Trust. The ruling, dated July 5 and entered in the public court record on July 7, refused to clear Sidley and its co-defendants of potential liability for allegedly helping Aequitas mislead investors.