There is nothing specific in the Constitution about bills signed by a usurper fraud posing as a real president.
I cannot understand why you think that a fake, a fraud, a mountebank, say not even a US citizen at all, would have the laws he signed while illegally tresspassing in the White House stand as though signed by an actual president.
It’s crazy talk.
If I became the president of Microsoft with a fraudulent resume and was not qualified to be president by their standards but was appointed by the board and I signed your paycheck, would your paycheck be valid?