According to whom? You? You're not the definer of valid federal action. The Constitution is and the Constitution gives Congress the power to legislate and impeach, but not "ultimate" power.
The Constitution is the Supreme law of the land and each Branch must honor and "preserve, protect, and defend" the Constitution as written and originally understood and intended. SCOTUS has a legitimate place in that role.
No not me, the Constitution. And in this situation the last resort is the people not the federal courts. If the Supremes had a role, for instance presidential appeal to the SCOTUS, the founders would have codified that avenue in the Constitution. Since they did not no such avenue exists. And no amount of wailing and stomping of feet gives the tyrants in black robes authority. And certainly no authority exists in the unelected federal agencies.