It was legislated law, by Congress and a president signing the bill.
Trump used an executive order, to stop a law that was on the US CODE books for years....by a stroke of the pen....and not requested by the people or the industry ordered to make them compliant with the law. Repubs used to be against that kind of stuff?
Biden zapped Trump's executive order, so the law on the books legally, could go back in place.
We have plenty of water where I am, though I suppose a hundred year drought could come? But if people really want the law to change, they can lobby congress to change it via legislation.
It complicates things for manufacturers if standards are set by states or regions and differ....it would take double the production lines and double inner components needed to acquire and stock to make them etc etc..... But it could be done with a year or two, lead time imo.