"I cannot undertake to lay my finger on that article of the Constitution which granted a right to Congress of expending, on objects of benevolence, the money of their constituents." -- James Madison, as he disapproved of an attempt to appropriate $15,000 for French refugees. 4 Annals of Congress 179 (1794).
I posted that quote a number of times while Congress was shoveling money at Katrina's victims. More than a few FReepers insisted I was terrible for doing so.
Too bad the constitution did not make it explicitly clear. Our founding fathers never dreamed that the Federal Government would have such power.