IANAL (obviously), so may be way off, but my understanding is that enforcement also involves interpretation here. So the law says a label is needed, but does the law require the recall, or not actually specify further. Would sending out stickers be acceptable? Would a printed warning to stock on shelves work? Are there exceptions available? Etc.

StillStackinAfterAllTheseYears

How is this related to the Chevron decision though?  If the law says the butter needed a label, the agencies are empowered to enforce that law.  Chevron is more about giving deference to agencies to 

Politics_And_Law

Costco recalled 80K lbs of butter because labels failed to say it contained milk

How is this related to the Chevron decision though?  If the law says the butter needed a label, the agencies are empowered to enforce that law.  Chevron is more about giving deference to agencies to *interpret* the law, not about enforcing it.