I don’t think the Senate could count on Justice or any other department under Obama’s thumb to help put pressure on the IRS. I do not believe that the Senate has any “independent” resources to use.
I find it impossible to believe that a corrupt, rogue Attorney General has the entire country under his boot.
I believe that any honest federal court judge can perform the task.
If Holder interferes, he's not only gone, but doing hard time.
Not to derail the thread, but Congress has the power to define what the Supreme Court may rule on ---- or NOT.