In short, the ruling means that states could set their own, perhaps stricter, energy efficiency regulations beyond the current federal regulations. The scenario opens the door for manufacturers to try to meet up to 50 different sets of rules, depending on where a given individual unit might be sold, instead of meeting a single set of federal guidelines. From there, you can see the manufacturing and logistical problems expand like Freon from a bad hose.
ARI's general counsel, Stephen Yurek, surmised that allowing the states to impose this additional layer of regulation "will eventually hurt U.S. manufacturers and drive jobs overseas."