The idea has begun to be floated that the debt limit is unconstitutional. The basic argument, according to this news account, is rooted in section 4 of the 14th Amendment, which requires that all outstanding public debt plus pension liabilities must be paid. The provision reads: "The validity of the public debt of the United States, authorized by law, including debts incurred for payment of pensions ..., shall not be questioned." Here is Garrett Epps' imagination of a speech by the President that presents Epps' idea of the meaning of this provision.
First, some definitional clarity is in order. The public debt authorized by law is the debt that has been issued and is outstanding and is within the statutory debt limit. The "debts incurred for payment of pensions" is somewhat less clear. It is reasonable to think that this phrase means the vested rights that have been acquired under current law for old-age pensions under Social Security, military pensions, and other federal pensions. But it does not mean the liabilities that are to be expected if and when future possible beneficiaries of such pensions become vested. Between the two categories -- public debt and pensions -- these are big numbers. But a refusal to raise the debt limit might not make it impossible for the nation to continue to meet these obligations. What it would mean is that all current revenue of the United States must first be devoted to paying the interest (and principal, when due) of the public debt and to continue to meet the vested rights of pensioners. Money left over can be spent on everything else. That would mean Draconian cuts -- in everything: Defense, EPA, Education Department, Labor Department, Justice Department, Medicare, Medicaid, welfare assistance of every stripe and kind, and the boondoogles of the budget. To the extent that current revenues are insufficient to meet the combined obligations of the public debt and vested pensions, perhaps the Epps argument is correct. But the 14th Amendment's public debt clause is not a license to continue to borrow above the statutory debt limit in order to continue paying for things that are not within the categories of vested pensions and public debt.
Of course, this situation creates another interesting conflict. The Impoundment Control Act denies to the President the ability to refuse to spend appropriated funds. But if the debt limit is not raised and current revenues are used to fulfill the obligations of the public debt clause, the President is forced to refuse to spend appropriated funds for other things because he has no statutory authority to borrow from the Chinese to get the money to spend these appropriated funds. Or, the President might contend that he is obliged to honor the Impoundment Control Act and violate the debt ceiling. One or the other of these statutes cannot be enforced under these hypothesized conditions.
A refusal to raise the debt limit does have constitutional consequences, but the public debt clause is not a grant of unlimited power to the President to borrow. A refusal to raise the debt limit, coupled with a refusal to cut current spending to levels that approximate current income, produces more political consequences than constitutional consequences.