The move recalls a similar fight over the definition of milk.

Can you call a sausage a sausage if it doesn’t contain pieces of livestock? A new law in Missouri says no—but civil liberties activists and a maker of vegetarian meat alternatives are fighting back.

Tofurky, an Oregon-based company that makes products such as a “chorizo style sausage” and “hot dogs” that contain no meat, on Monday sued to block the new law, which takes effect on Tuesday. It was joined in the suit by the Good Food Institute, the American Civil Liberties Union of Missouri and the Animal Legal Defense Fund.

The lawsuit hinges on the idea that the Missouri law infringes on First Amendment rights to free speech. It also alleges that the law illegally discriminates against out-of-state companies in order to protect meat producers based in Missouri.

“Missouri is putting its thumb on the scale to unfairly benefit the meat industry and silence alternative producers,” said Stephen Wells, the executive director of the Animal Legal Defense Fund, in a statement.

The plaintiffs said in their statement that “no one buys Tofurky ‘plant-based’ deli slices thinking they were carved from a slaughtered animal any more than people are buying almond milk thinking it was squeezed from a cow’s udder.” The latter point is actually contentious—the Food and Drug Administration (FDA) recently decided to crack down on the use of the term “almond milk” on the basis that “an almond doesn’t lactate.”

However, some of those who pushed for the law claim they weren’t trying to target companies such as Tofurky—instead, they were concerned about the new trend of lab-grown “meat.”

When the new “Missouri Cattlemen’s Fake Meat Bill” cleared the state legislature in May, the Missouri Cattlemen’s Association (MCA) said it expected its counterparts in other states to push for similar laws.

“I never imagined we would be fighting over what is and isn’t meat,” said MCA Vice President Mike Deering at the time. “It seems silly. However, this is very real and I cannot stress enough the importance of this issue.”

“Americans don’t like censorship, and they don’t like the government picking winners and losers in the marketplace,” said Bruce Friedrich, the executive director of the Good Food Institute. “We’re confident that the court will overturn this anti-competitive and unconstitutional law.”

Sales of plant-based meat alternatives rose by almost a quarter in the last year, according to data released at the end of July. Advocates say non-meat products are healthier and better for the environment, and the likes of Bill Gates and Richard Branson—and even meat production giant Tyson—have invested in “clean meat” startups that grow meat in tanks.