The nation’s state legislatures have a request for their federal counterpart: pass a farm bill this year, but first remove a controversial provision that restricts state powers.

In Play's Jackie Kucinich breaks down the five big Farm Bill issues Congress needs to sort out before January. (The Washington Post)

The measure, championed by industry and criticized by states and animal-rights groups, would neuter the ability of states to regulate the way food is made by prohibiting laws that affect products coming in from out of state.

It would “erode state sovereignty by preempting state laws protecting our nation’s food production and manufacturing as well as increase state administrative costs,” the National Conference of State Legislatures, a bipartisan group that represents the nation’s state legislative bodies, wrote in a Tuesday letter to the leaders of the House and Senate agriculture committees.

Nicknamed the “King Amendment,” after sponsor and longtime tea party caucus member Rep. Steve King (R-Iowa), the provision has come under fire for producing what some say amounts to a radical shift in the power dynamic between states and industry.

King’s amendment, a piece of the farm bill the House passed earlier this year, would preempt a set of regulations governing humane treatment of animals passed by California’s voters in 2008.

That ballot measure, which King says enforces “unreasonable and arbitrary” standards, would require “that calves raised for veal, egg-laying hens and pregnant pigs be confined only in ways that allow these animals to lie down, stand up, fully extend their limbs and turn around freely,” according to an official state summary of the law. The rules governing egg-laying hens are set to go into effect in 2015.

In their letter, the state legislatures argue that they “have used this authority to enact laws that protect their citizens from invasive pests and livestock diseases, maintain quality standards for all agricultural products and ensure food safety and unadulterated seed products.”

But the federal government already protects citizens, King wrote in a June National Cattleman’s Beef Association newsletter.

“Regardless of how they’re produced, eggs are already regulated by the Federal Egg Inspection Act, which ensures all eggs entering interstate commerce are safe for the consumer,” he wrote.

King’s home state of Iowa is the nation’s largest egg-producing state by a wide margin, accounting for more than one in seven eggs produced in the United States, according to the Department of Agriculture.