[DuxFan4ever]

... but conveniently forget about telling the people they can't fund it.

They can't fund it? How do you know this? Congress can give itself the authority to borrow as much as they want. If they weren't allowed to go into the red, the US either would be in default right now or there would be some serious spending cuts.

[tobyhill]

It would have to go into a supplemental spending bill since the budget is already passed or wait till the next budget cycle. They could barrow against some other budget but that would take an act of congress.