A judge on Monday set a tentative July trial date in the dispute between Sallie Mae and an investor group seeking to terminate its proposed $25 billion buyout of the student lender.

Vice Chancellor Leo Strine Jr., of the Delaware Court of Chancery, said the trial date could be pushed back if Sallie Mae wants a preliminary ruling on whether legislation enacted after it agreed in April to be bought out by a group led by private-equity firm J.C. Flowers & Co. represents a material adverse effect, nullifying the deal.