In this article at CNN, Robert Hockett, a law professor at Cornell University says that the debt ceiling was rooted in the 1917 Liberty Bond Act which was rendered obsolete in 1974.
Part quote from the article, from under the question "Why presidents actually have the power to ignore Congress’ artificial debt ceiling"
HOCKETT: Yes. It’s not only artificial, but I think it’s also legally invalid. The only reason we haven’t heard that definitively from the courts yet is that both parties have benefited, I think, from the grandstanding opportunity that it affords them.
The bottom line here is the 1917 Liberty Bond Act, in which the debt ceiling is rooted, was rendered obsolete in 1974.
It seems that Hockett is referring to the Congressional Budget and Impoundment Control Act of 1974
But if above is correct, it is surprising that even this explainer page published by the White House does not mention it. Rather the explainer page says
Once the debt limit is hit, the Federal government cannot increase the amount of outstanding debt; therefore, it can only draw from any cash on hand and spend its incoming revenues.
When the U.S. Treasury exhausts its cash and extraordinary measures, the Federal government loses any means to pay its bills and fund its operations beyond its incoming revenues, which only cover part of what is required (about 80 percent in 2019).
Because the United States has never defaulted on its obligations, the scope of the negative repercussions of not satisfying all Federal obligations due to the debt limit are unknown; it is expected to be widespread and catastrophic for the U.S. (and global) economy.
U.S. government officials recently made similar statements.
What is the reason for all the warnings about the failure to raise the debt ceiling if it was invalidated in 1974? I mean, would the invalidation need to be legally validated somehow and is there a risk that that might not happen, or are there other reasons?