When Rep. Steve King slipped an amendment into the House farm bill that would undo state laws protecting farm animals, liberal and animal-rights groups not surprisingly jumped on the Iowa Republican. State lawmakers also opposed the measure, calling it a federal intrusion of state rights.

Now another large and influential group is upset at the outspoken congressman over his measure: the police.

King’s amendment would prohibit states from establishing certain animal welfare standards for commercial agricultural products — such as eggs or beef — that are produced in one state but sold in another.

But the Fraternal Order of Police has complained that the measure, if it becomes law, would “allow for the proliferation of puppy mills, dog and cock fighting, kill shelters and other animal cruelties.”

King, who also caused waves this summer after accusing young illegal immigrants of being drug smugglers, said his legislation would strike down state laws that lead to “onerous” agricultural production methods that drive up food costs. He particularly targeted California laws that, among other things, bar the sale of eggs unless chicken pens are of a certain size.

But in a letter to King this week, Chuck Canterbury, the Fraternal Order of Police’s national president, said the lawmaker’s measure would increase “criminal enterprises” that often go along with these activities and make investigating the crimes more difficult.

“The amendment would not only endanger animals but would also preempt state laws and regulations,” he said. “If your language remains part of the legislation, animals will be at a greater risk of mistreatment.”

King’s measure was included in the farm bill that passed the Republican-controlled House in July. But the measure likely will die in the Democratic-run Senate, which passed its own version a month earlier.