Article 1 section 9 clause 7 denies the federal government the power to spend money unless congress passes a law allowing it.
This is the actual article:
"No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law; and a regular Statement and Account of the Receipts and Expenditures of all public Money shall be published from time to time."
As you can see here, there will be repercussions if the federal government doesn't abide by laws.