Hi.
They can request until the cows come home, but the President has the authority to seal the records by executive order.
Then the case will likely go to SCOTUS.
5.56mm
I think that the USSC will see this law as being unconstitutional. It has never been tested and it would violate the 4th, 5th and 14th amendment. If they believe a crime has been committed they can refer it to the DOJ. If they want it for legislative purposes they will need to show that the detailed, (verses a synopsis), tax return is necessary for creating laws. I can see the USSC saying that the IRS can provide a summary, without $ amounts, which deals with specific laws they feel may need amending or new laws that may need to be proposed/passed but not the detailed, line by line tax return.