They made the argument in front of U.S. District Judge Lynn Winmill during a Wednesday hearing.
Attorneys representing a coalition of free speech, environmental and animal right activists countered that deception is protected speech as long as it doesn't directly cause harm.
The two parties are arguing over the constitutionality of a recently passed law that prohibits individuals from going undercover to investigate animal abuse or other problems at agricultural operations. Gov. C.L. "Butch" Otter signed the bill Feb. 28, and due to an emergency clause, the legislation became effective immediately.
The statute, dubbed the "ag-gag" law, makes it illegal to surreptitiously record audio or film activities on private land without permission. Violators could face up to a year in jail and a $5,000 fine.
"Recording is a medium of expression and limitations on it is a form of discrimination," said Justin Marceau, a law professor at the University of Denver working with the American Civil Liberties Union of Idaho on the lawsuit. Marceau is also counsel for a group who last July filed a similar lawsuit against Utah's farm protection law.
Courts have already decided that deliberately misrepresenting one's background which is prohibited under the controversial law for any agricultural worker did not amount to fraud, Mareau said.
Marceau also pointed out that the law is too broad in scope. While it says it applies to agricultural facilities like dairies and farms, the way it is written would be applicable in a Home Depot and Costco because those stores handle products like pesticides, he said.
Idaho lawmakers passed the anti-secret filming statute two years after private animal activists released footage of animal abuse on one of Idaho's largest dairies. Los Angeles-based Mercy for Animals recorded footage of employees stomping on cows, beating them with a pink cane and dragging one cow with a chain around its neck by a tractor.
Idaho Deputy Attorney Clay Smith said the law protects property owners' rights to determine who should or should not be allowed on their land.
Responding to Winmill's question if the law infringes on the media's rights, Smith said that press members are subject to ordinary law just like the public.
"You can't use the First Amendment to walk around basic private property rights," Smith said.
Winmill said he will make a decision whether to dismiss the case in the next few weeks.
"There's a lot to think about in this case," he said. "All five sections and subsections of the law raise their own separate issues. Some of which I feel fairly comfortable, while others I'm still muddling around."