The US Supreme Court has rejected an appeal by Enron investors pursuing investment banks that put together financing deals for the energy trader.
Other investment banks have reached out of court settlements
The justices refused to hear arguments in the $40bn (£20bn) class-action suit linked to the 2001 collapse of Enron.
The banks were Merrill Lynch, Barclays and Credit Suisse First Boston.
The rejection had been expected after a ruling last week in another securities fraud case that limited the ability of shareholders to pursue third parties.
"Fundamentally, it means it's over," said Jay Brown, a securities law professor at the University of Denver's Sturm College of Law.
But lawyers for the shareholders said they would return to the federal court in Houston in an attempt to prove that the investment banks misled the public about Enron's financial condition.
The collapse of Enron, which was the seventh largest US company, wiped out thousands of jobs, more than $60bn in market value and $2bn in pension plans.