Story highlights The case focused on a state law in California

The law mandated "humane treatment" of downed livestock headed for slaughter

Several justices had earlier noted the good intentions behind the state action

The court holds that interstate commerce is federal jurisdiction, trumping state efforts

A state law mandating "humane treatment" of downed livestock headed for the slaughterhouse was unanimously overturned Monday by the Supreme Court.

At issue was whether federal regulations dealing with inspection of domesticated animals about to be killed, processed, and sold for human consumption preempted -- or nullified -- California Penal Code 599f.

Several justices had earlier noted the good intentions behind the state action, but all now agreed that it went too far into the traditional federal arena.

"The Federal Meat Inspection Act regulates slaughterhouses' handling and treatment of non-ambulatory pigs from the moment of their delivery through the end of the meat production process," wrote Justice Elena Kagan. "California's (law) endeavors to regulate the same thing, at the same time, in the same place -- except by imposing different requirements. The FMIA expressly preempts such a state law."

That state law became effective in 2009, following shocking undercover video released by the Humane Society. Slaughterhouse workers in San Bernardino County outside Los Angeles were shown dragging, prodding and bulldozing weak, "non-ambulatory" cows into slaughter pens. Water from hoses was used on some cattle lying on their sides, to force them to their feet.

Penal Code 599f would require meat processors to immediately remove downed animals and "humanely" euthanize them. And the sale, purchase or shipment of such animals would be criminally prohibited.

The long-standing Federal Meat Inspection Act also requires animals lying down to be removed, but gives discretion to federal inspectors to determine whether the livestock can recover sufficiently and become fit for slaughter and human consumption. That law expressly prohibits any state regulation "in addition to or different from" the federal requirements. It includes cattle, pigs, sheep and goats.

The Supreme Court has long ruled that interstate commerce is under federal jurisdiction, trumping any state efforts to regulate it.

The current case was brought by a meat trade group on behalf of pig farmers in California. The Obama administration sided with pork producers, a move criticized by a number of animal rights groups.

A federal appeals court in San Francisco last year had ruled in favor of the state law, labeling as "hogwash" an earlier judge's decision that favored the industry.

The law's enforcement has been put on hold pending the Supreme Court's decision, now in legal support of the industry.

Animal defenders blasted the high court's ruling, and urged the federal government to step up its enforcement and monitoring of slaughterhouses.

"This is a deeply troubling decision, preventing a wide range of actions by the states to protect animals and consumers from reckless practices by the meat industry, including the mishandling and slaughter of animals too sick or injured to walk," said Wayne Pacelle, president of the Humane Society of the United States. "The fact is, Congress and the USDA have been in the grip of the agribusiness lobby for decades, and that's why our federal animal handling and food safety laws are so anemic. California tried to protect its citizens and the animals at slaughterhouses from acute and extreme abuses, but its effort was cannibalized by the federal government."

Pork producers in their legal brief estimated that about 3% of swine are non-ambulatory when they arrive at the slaughterhouse. Most of the downed beasts, they say, are merely overheated, fatigued or stubborn, and most are soon back on their feet. Animal rights activists challenge that assertion.

The meat industry argued being forced to immediately euthanize all downed animals would hurt its ability to detect and fight one particularly virulent disease: foot-and-mouth, which is highly contagious. The industry says federal inspection is preferred, since pre-slaughter inspections of sick animals are required. The state law would mandate immediate killing and disposal of the lying-down livestock.

California -- backed by animal rights groups -- also contended the two laws were compatible, allowing local conditions to be addressed and ensuring that moral and humane conditions would be part of meat processing rules.

The case is National Meat Association v. Harris (10-224).