With the deadline looming for raising the debt ceiling, there’s one important thing to understand about the debate over the Constitutional status of the debt limit: if Congress does not act soon, and if the Treasury Department cannot come up with any more tricks and gimmicks to avoid default or technically taking on more debt, then Barack Obama will have no choice but to violate the law — and, perhaps, the Constitution.

First, the law. On August 2 or thereabouts, the United States Government will hit the statutory debt limit, and therefore not be allowed, under the law, to borrow more money. Paying the government’s debts is a legal obligation. But the president is also legally obligated to spend money on government programs: On Social Security, Medicare, regular annual appropriations, and anything else that Congress has mandated. There isn’t enough money to do both unless the U.S.A. can keep borrowing — which would become illegal if the debt ceiling isn’t raised. Therefore, if it isn’t raised, Obama will have no choice but to violate one of those obligations.

The desire to avoid this predicament is why people have been rethinking the constitutionality of the debt limit. Here there are two competing provisions. Article I, Section 8, Clause 2 says that Congress has the power “to borrow money on the credit of the United States.” The debt limit is Congress’s way of doing that; it authorizes borrowing money up to a certain point, but no farther. However, as Bruce Bartlett has been pointing out for a while now, the 14th Amendment says that “The validity of the public debt of the United States, authorized by law…shall not be questioned.” Put the two together, and this may mean that Congress may not, under the Constitution (since the addition of the 14th) authorize spending and revenue levels that will produce debt but then tell the president he may not borrow. For those who want (a lot) more, see here, here, and a dissenting view here .

Can Article I and the 14th Amendment be reconciled? I don’t know. What I do know is that Congress will have put the president in an impossible position if there’s no debt limit increase by the deadline. If he chooses to interpret the 14th as invalidating the debt limit — along with an interpretation that Congress, by obligating spending without revenues to pay for it, in effect de facto asked for more debt regardless of the statutory limit — well, it’s certainly not an unreasonable position.

On top of that, I agree with Jonathan Zasloff:if the president does choose to ignore the debt limit (as opposed to ignoring the legal obligations to spend and pay debts — remember, he has to do one or the other) then it’s relatively unlikely that anyone would have standing to take the case to court. At least, that’s what Zasloff argues that recent Supreme Court decisions would imply. As we all know (ahem, Bush v. Gore), the Supremes have been known to adjust when the politics of the situation called for it, in their view. If that’s correct, the only real recourse for Congress would be impeachment, and note that at least some conservatives already see trying that as a legitimate response. (Not that they could get conviction in the Senate.)

Regardless of your interpretation of the legal situation, Congress is about to leave Barack Obama no choice but to violate some obligation. That’s the crucial context you need to understand the legal arguments that you’re going to hear plenty of in the next few weeks.