It's easy to assume that partisan squabbling defines every dispute in Congress.

This editorial, however, is about a subject that may defy the usual Democrats vs. Republicans storyline: states' authority to enact laws governing food safety and farming practices.

Beginning in 2015, barely 13 months from now, a voter-approved law requires California farmers to provide hens, sows and veal calves with enough room to move — to stand or lie down, to turn around or extend their limbs — in their pens.

A bill sponsored by then-Assemblyman Jared Huffman, D-San Rafael, extends the Proposition 2 requirement to eggs, pork products and veal shipped into the state for sale.

Since then, egg farmers across the country have joined with animal welfare organizations to support a national standard based on California's law.

But an Iowa congressman from a major egg-producing district is instead working on behalf of cattlemen and pork producers to undermine Proposition 2 and any similar state law.

GOP Rep. Steve King, who denounces animal rights advocates as the "vegan lobby," managed to place a poison pill in the House version of the Farm Bill. His amendment would bar states from extending food safety and animal protection standards to products imported from other states. The Senate version of the Farm Bill has no such language, putting the issue on the agenda of a two-house conference committee that is working to reconcile the bills.

King's amendment may seem like a sideshow in a debate over a $1 trillion bill that also covers food stamps and farm subsidies (a major source of income for King's constituents). But the amendment threatens to create a "race-to-the-bottom" approach to food safety, and it must be deleted from the Farm Bill.

Fortunately, that isn't lost on some of King's fellow House Republicans. Rep. Jeff Denham, R-Turlock, is a member of the conference committee, and he makes a succinct but strong case against King's provision.

"Finally," he wrote in an op-ed about the Farm Bill published last week by the Tracy Press, "it is imperative that we uphold states' right to protect their own individual agriculture industries by passing laws related to safety and agriculture production.

"We must fight to strike the King amendment from the Farm Bill, as it tramples on the 10th Amendment to the U.S. Constitution and imperils the fate of California egg producers. The amendment, if passed in the Farm Bill, would not only nullify many California food safety laws, but it also would affect food safety laws nationwide — laws that regulate tobacco, pest management, livestock entry requirements and dairy standards."

Echoing that view, the bipartisan National Conference of State Legislatures says King's amendment would "erode state sovereignty by preempting state laws protecting our nation's food production and manufacturing as well as increase state administrative costs." In other words, King would create a one-size-fits-all federal rule, which is the opposite of what Republicans usually support.

If Kings succeeds, Arnie Riebli, a Petaluma egg farmer active in agriculture organizations, has told us California farmers would be forced to fight the new animal welfare rules. "And," he said, "we don't want to."