What's confusing about my response? Broom asked for a government site, of which OOIDA is not, where Bush signed the bill into law. The site I provided is a government site that is all about when and where Bushed signed the Bill.
The pertinent text of the law can be found here, #12 on the list:
US CODE: Title 23,127. Vehicle weight limitations—Interstate System
When I read it at the time it was a Bill, and again now, I really can't see how it can be interpreted to be left up to the states on whether or not to adopt it, especially when combined with the FMCSA part
658.17 (near the bottom)