Although products like veggie burgers and sausages have been sold for years, the debate over how they can be described has become particularly contentious as plant-based products have grown more popular. This has created a challenge for the traditional meat industry, prompting debates about whether something without eggs can be called mayo and whether almonds lactate. Butchers in France have even sought protection against veganism.

The value of the market for meat substitutes in the United States has grown from about $556 million in 2012 to $699 million last year, according to Euromonitor, a consumer research company. This is still just a portion of the $29 billion processed meat industry, but it has been growing fast enough for big food businesses to take notice. The meat processor Tyson Foods took a stake in a company that makes “meat” from soy and peas in 2016, and the agribusiness company Cargill signed a joint venture agreement with a producer of plant-based proteins earlier this year.

In Missouri, supporters of the new law argue that consumers may be confused about these new products. “Making sure that consumers knew what they were buying was the whole intent,” said Mike Deering, the executive vice president of the Missouri Cattlemen’s Association, of the state’s law. “You cannot market a station wagon as a Porsche.”

But for Jaime Athos, the chief executive of Tofurky, this is just a case of protectionism. His company has no interest in being mistaken for a traditional meat producer and has “bent over backward” to make sure that customers know that their products do not come from animals. “That’s the selling point,” Mr. Athos said.

Mr. Deering noted that the legislation had been spurred more by the development of lab-grown meat than by clearly labeled veggie burgers. “We have problems with products that piggyback on products that our families have put their blood, sweat and tears into,” Mr. Deering said, adding that the risk to his industry could be huge if there were ever a safety issue with lab-grown meats.