White Leghorn egg-laying chickens in cages in their hen house. (istockphoto)

An interstate feud over chicken coops ended with a federal judge last week siding with a California law that seeks to force producers to provide humane living spaces for egg-laying hens.

U.S. District Court Judge Kimberly Mueller dismissed a lawsuit Thursday brought by Missouri and five other states that sought to overturn the California law, passed in 2010, that requires all eggs sold in the Golden State to come from chickens that are treated humanely. The California law requires chickens to be kept in coops big enough for them to stand up, lie down and extend their wings.

Missouri Attorney General Chris Koster (D) filed suit against California this year, arguing that it ran afoul of the U.S. Constitution’s interstate commerce clause because it would have imposed new and costly regulations on out-of-state producers. Koster said the law would require Missouri farmers to spend upwards of $120 million to build new facilities to comply with the law.

“California has placed restrictions on the sale or transfer of a commodity based on production methods that have nothing to do with the health or safety of California consumers,” Koster said when he filed suit. “If California legislators are permitted to mandate the size of chicken coops on Missouri farms, they may just as easily demand that Missouri soybeans be harvested by hand or that Missouri corn be transported by solar-powered trucks.”

Attorneys general in Alabama, Kentucky, Iowa, Nebraska and Oklahoma joined Missouri in seeking relief.

But Mueller was unconvinced that the law would do actual harm to citizens in those states. She tossed the case because the states lacked standing to sue California over a law she said would harm only a small subset of egg producers who export their eggs to California.

The California law came from a 2008 ballot initiative that required animals, not just chickens, to be treated humanely. Proposition 2, which passed with 63 percent of the vote, mandated healthier treatment for calves, hens and pigs.

California egg producers worried that the law meant they would be at a disadvantage when competing with out-of-state producers that weren’t subject to the same rules. The state legislature passed a companion bill in 2010, signed into law by then-Gov. Arnold Schwarzenegger (R), that required those out-of-state producers to uphold the same standards.

The Humane Society of the United States, which helped defend the California law, argued that producers in other states had plenty of time to comply before the law goes into effect at the beginning of January, five years after Schwarzenegger signed the bill.

“Any egg producer is going to have to comply with animal welfare conditions that California passed. It really does have the potential to affect millions of animals’ lives,” Rebecca Cary, a staff attorney at the Humane Society, told the Alabama Media Group.

Producers in other states don’t actually have to build new facilities, but they would be barred from selling their wares in California if they don’t. That’s a huge risk for the industry, though: Californians import about 4 billion eggs a year, according to Humane Society statistics.

And the law does not apply to all egg producers; it only applies to shell eggs, like the ones in 12-packs at grocery stores. Producers who make egg products, like egg whites or liquid products, don’t face the same restrictions.

The Missouri suit is the latest in a string of litigation against the California law. Rep. Steve King (R-Iowa) has tried to insert an amendment into the Farm Bill and other legislation that would prohibit states from imposing standards on agricultural products from out of state if the standards are stricter than those imposed by the federal government. Three other lawsuits have been filed against California, all of which have failed.

Koster’s office said Friday that it would review Mueller’s decision before choosing how to proceed.