A federal judge stood up for free speech in striking down an Idaho “ag-gag” law that criminalizes the undercover recording of farming operations.

Six other states – Montana, Utah, North Dakota, Missouri, Kansas and Iowa – have such laws. North Carolina adopted one that goes into effect next year. Some legislators in Olympia expressed interest last year, but this ruling ought to be seen as a death knell.

U.S. District Judge Lynn B. Winmill cited violations of the First Amendment and the Equal Protection Clause of the 14th Amendment. The state hasn’t decided whether it will appeal, but overcoming those constitutional concerns won’t be easy.

It shouldn’t be.

The ag-gag law in Idaho was a reaction to the surreptitious video recording by Mercy for Animals, an animal welfare group. The video depicted workers at a southern Idaho dairy farm gratuitously and gruesomely abusing cows. Activists then denounced dairy operations and called for boycotts.

The Idaho Dairy Association characterized this activity as interfering with the production of an agricultural product and lobbied for a law against it. When First Amendment concerns were raised, supporters of the bill were incredulous that covert recording by people who misrepresent themselves could be protected speech. That’s an interesting position in light of the secret recordings of Planned Parenthood officials by activists operating under false pretenses. Few, if any, Idaho legislators would support a gag law in that instance.

The journalist Upton Sinclair used subterfuge to expose the slaughterhouses of Chicago. His book spawned the Pure Food and Drug Act and the Meat Inspection Act. Under Idaho’s ag-gag law, he could’ve been tossed in jail for a year.

Ag-gag proponents say the law is necessary to protect privacy and property rights, but there’s already a law against trespassing. Proponents say they need the law to counter the lies and distortions of activists. But that’s what defamation laws are for.

The law runs afoul of the Equal Protection Clause because it’s focused solely on the agriculture industry. The drafter of the legislation complained that undercover operations exposed the industry to “the court of public opinion.” Many industries would love to be shielded from that, but government is supposed to ensure equal protection, not extra protection.

In the court of public opinion, you may call this newspaper a “fish-wrapper” without fear of being arrested. That’s how it should be.

The Idaho Dairy Association is urging the state to appeal the ruling, but that would be an unwise expenditure. The state already tilted at the gay-marriage windmill in federal court and lost big. On Monday, a federal magistrate ordered Idaho to pay another $223,000 in attorneys’ fees to the four couples who won the case. That’s on top of the $401,000 it already paid.

In both cases, Idaho fought the U.S. Constitution and lost. Move on.