A new GMO labelling law in Vermont is sending ripples through the North American food industry.

Starting July 1, processed foods sold in the state that contain genetically engineered ingredients must say so on the label.

Similar laws exist in countries across Europe, but for now, genetically modified organisms don't have to be labelled in the rest of the U.S., or in Canada.

David Zuckerman, an organic farmer and Vermont state senator who pushed for the law, said people in his state want to know where their food comes from. The new law will allow them to decide whether or not they want to buy GMO foods.

"With a labelled product, consumers can make that decision," Zuckerman said.

At a grocery store in Georgia, Vt., staff members have been busy making sure the products they sell comply with a new law, which comes into effect across the state July 1.

David Zuckerman is an organic farmer and the Vermont state senator who pushed for the law. (Alison Northcott/CBC)

From canned soup to bags of chips, new labels reading "prepared with genetic engineering" must now appear on packaged foods made with ingredients that contain GMOs.

"I'd like to know the origin of food before we put it in our body," said Erica Wiggins, as she shopped for groceries with her two children.

"It just seems so simple and it seems necessary."

Some food giants opposed

The law, which passed in 2014 and is only now coming into effect, has faced opposition from some food companies.

Opponents argue the new rules will hurt Vermont farmers who grow GMO crops and stigmatize products the U.S. Food and Drug Administration says are safe.

The Grocery Manufacturers Association, which represents big-name food brands, sued Vermont to try to block the law, but lost.

Food policy expert Sylvain Charlebois says while similar laws could come into effect elsewhere, more consumers are getting comfortable with buying food with GMO content 4:14

Now, companies could face fines of up to $1,000 US a day for each item that does not have the proper label.

Others have changed their labels to identify genetically engineered ingredients in products across the U.S.

"We can't label our products for only one state without significantly driving up costs for our consumers and we simply will not do that," cereal-maker General Mills said in a statement on its website.

Other food companies, however, have stripped their products of GMO ingredients altogether. Chris Miller, the activism manager at Ben and Jerry's, said it's a process the ice cream maker started before the law passed.

Campbell Soup Company supports federal legislation for a single mandatory labelling standard for foods derived from genetically modified organisms. (Jessica Rubinger/CBC)

"Given the fact that consumers were concerned about the use GMOs in food supply chains, given the fact that there was this was this big push to know and disclosure of genetically-engineered ingredients, we just felt that it was the right thing to do," Miller said.

For his part, Jim Harrison, head of the Vermont Retail and Grocers Association, said he's been fielding questions from worried store-owners and has even offered webinars outlining what they need to do to comply.

The association is not against labelling GMOs, but says given Vermont's tiny share of the market, its law just isn't practical.

"Some products may not be available and there may confusion in the market place," he said.

N ationwide rules?

With other states poised to create their own laws, there are calls for a uniform set of labelling rules that would apply across the United States.

U.S. Congress is considering a more lenient bill, backed by the food industry, for voluntary GMO labelling. Under the proposal, producers would have the choice of printing the information on a label or making it available through a smartphone, or 1-800 number.

Producers and retailers say it would prevent a patchwork of different laws across the country.

A harvester works through a field of genetically modified corn near Santa Rosa, Calif. (Rich Pedroncelli/Associated Press)

But if that passes, Vermont's law would be nullified and replaced by a law that David Zuckerman, the state senator, says is too weak.

"All the proposals that have come out of Washington so far have not been transparent," he said.

"All [are] obtuse ways for people to learn the information, versus very clear labeling that Vermont requires."

For its part, Canada does not require labelling of genetically modified organisms in foods, but the NDP has been calling for mandatory labelling across the country. Quebec is considering its own legislation, and the province's Agriculture Minister Pierre Paradis has been watching Vermont's efforts closely. He is in Vermont today to participate in official celebrations marking the law's first day.