Congress can appoint a special prosecutor.
But it will not happen because of what Freeper sundance has well-described as an effort by both parties to bury the illegal gun running for profit that would land many members in leadership on both sides in the crosshairs of a special prosecutor.
It could happen if the American people were as passionate about prosecuting Hillary as they are about securing the border. But it’s hard to get the electorate worked up about something that does not affect them directly or locally. It’s clearly wrong but it’s more a case of increasing the public’s distrust of the system rather than a direct passionate crusade. So it defaults to Congress to do something about it but they won’t. The result will be that Gowdy will be seen as a member of the establishment, all talk no action.
Congress has no prosecutorial powers at all. The only punitive power they have is the power to impeach.