The Permanent Subcommittee on Investigations wants to use the multibillion-dollar trading loss by JPMorgan Chase & Co. to push regulators to reinforce the Volcker rule. One of the many questions is JPMorgan's bets on derivatives could have been prevented under regulator's first draft of the rule's ban on proprietary trading. The ban was inserted in the Dodd-Frank Act, but left the details up to regulators.