(CNN) -- Vermont's governor on Thursday signed a bill into law that will require the labeling of genetically modified foods -- hailing it as the first such law in the nation.
Under the new law, food offered for retail sale that is entirely or partially produced with genetic engineering must be labeled as such by July 2016.
"Vermonters take our food and how it is produced seriously, and we believe we have a right to know what's in the food we buy," said Gov. Peter Shumlin. "More than 60 countries have already restricted or labeled these foods, and now one state -- Vermont -- will also ensure that we know what's in the food we buy and serve our families."
In the absence of federal action, other states have introduced similar legislation or ballot initiatives, according to the non-profit Center for Food Safety.
Maine and Connecticut passed laws requiring labeling, but they won't go into effect until other states pass GMO-labeling laws. Vermont is the first to pass a "no strings attached" bill, the watchdog group said.
Supporters of the law expect it will be challenged in court.
"I can make no predictions or promises about how the courts will ultimately rule but I can promise that my office will mount a vigorous and zealous defense of the law that has so much support from Vermont consumers," said Vermont Attorney General William Sorrell.
The governor tweeted: "Those opposed will put up a fight. Help us fight back."
Cathleen Enright, executive vice president for food and agriculture for the Biotechnology Industry Organization, a trade group, warned that mandated labeling could make food costs for the average household could go up as much as $400 a year.
She stressed foods made from genetically modified crops are as safe as any other.
"And these same GM crops have enabled farmers to produce more on less land with fewer pesticide applications, less water and reduced on-farm fuel use," Enright said in a statement.
The U.S. Department of Agriculture Food Safety and Inspection Service approved a non-GMO label for meat and liquid egg products in June, the first time the department has approved such a label from a third party.
GMO foods were approved for human consumption in 1995, but the Food and Drug Administration never required any labels pointing them out as such.
CNN's Eliott C. McLaughlin and Kevin Conlon contributed to this report.