Amid a financial crime spree and spate of corporate convictions, federal regulators recently floated a proposed fix: strengthening an existing rule designed to bar criminal banks from managing — and profiting off — trillions of dollars of retirement funds.

The idea seemed simple enough: banks would be deterred from committing crime by the prospect of losing lucrative business, and American workers would be better assured that their retirement money wasn’t being managed by literal criminals.

And yet despite the idea being grounded in long-standing law, the new initiative has prompted a Wall Street freak-out. In recent weeks, financial behemoths have deployed an army of lobbyists to try to block the proposal, and prevent the government from making sure criminals are not skimming fees from millions of retirees.