The court heard appeals Wednesday from the National Meat Association, which wants a 2009 California law blocked from going into effect.

The law bars the purchase, sale and butchering of animals that can't walk. It requires slaughterhouses to immediately kill nonambulatory animals.

The association sued, saying state law interferes with federal laws that require inspections of downed livestock before determining whether they can be used for meat.

A federal judge agreed and blocked the law, but the 9th U.S. Circuit Court of Appeals threw out the hold.

Chief Justice John Roberts said state laws cannot say downed animals can't be sold as meat when federal law says that they can.