Some worry the labelling could stigmatise GMO crops and could reduce demand for food containing genetically modified ingredients.
The labels tell consumers exactly where their food comes from.
But ingredients such as beet sugar and soybean oil, which can be derived from genetically modified crops but contain next to no genetic material by the time they are processed, may not fall under the law's definition of a bioengineered food
This issue is all about consumers' choice, argues Liz O'Neill, the director of GM Freeze, an organisation that campaigns against GM food.
"It's not used responsibly, fairly or sustainably, so there are issues coming to play and consumers want to express their choice, they want avoid genetically engineered food and the only way they can do that is through the labelling of food product," she told RFI.
"People will tend to choose organic products if they can but that's not always an accessible choice so it's really really important that food is labelled. And we can see the impact of that in the uptake of GM, certainly in the UK, there's very few GM products on the shelves and they don't sell well, whereas in America, where GM products are not labelled, they're absolutely the norm in non-organic food."
Fit for human consumption?
Debate still rages as to whether GMO foods can be declared safe for human consumption.
"The National Academies of Science issued a report that did state that, so far, there is no scientific proof that they cause health problems. It also said that, given the complexity of the technology, it is too early to have a definite answer," says Marco Contiero, the policy director on agriculture for Greenpeace in Europe.
"And most importantly, it said that GMOs have not shown to yield more than non GM plants, which means that it has debunked the myth that GMOs produce more."
Activists argue that greater use of GM seeds means greater use of pesticides.
"There is one myth that the industry keeps hammering on: we need to grow GM crops to feed the world. First of all, the vast majority of GMOs are just used to feed animals or [make] biofuels, this is a fact," Contiero said.
These crops fit perfectly with an industrial agricultural system which is responsible for many of today's problems, he claims.
"It relies on monocultures, genetically identical plants which are actually dependent on accelerated inputs for example pesticides, herbicides, fertilisers, fossil fuels, of course, to operate machinery. Such a system is not a system that will allow us to have a sustainable development."
There are also concerns that labelling could have a negative economic effect.
When the European Union started the practise 15 years ago costs did rise, but only slightly.
"It's been demonstrated that the labelling in Europe did cause a price increase because of its additional burden on manufactures, for example if they don't want to mix all products together etc, it adds complexity to the market, it adds complexity in storage, then in tracking, warehousing. So the costs were slightly higher, not by a large margin, but noticeable," Markus Lipp, the senior officer of food safety at FAO, told RFI.
But the economic effect could be positive in some respects, according to labelling advocates.
"At the moment companies that use GMOs cannot export to Europe because the food market is closed because no company would take the risk to have products labelled as GMOs on the shelves of European supermarkets," Eric Gall of the International Foundation for Organic Agriculture told RFI.
"When the GMO labelling was introduced in Europe 15 years ago, actually the US lost many exports markets to Europe because European consumers did not want to have GMOs in their product and they could know whether they were in their product or not. So, if there ismandatory GMO labelling in the US, this could have positive consequences for the US food industry."
It remains to be seen what effect GMO labels will have but they will at least enable people to choose what they want to put on their plates.