There may have been fewer than 20 of them on the street, but a group of demonstrators in Paris has nonetheless made the national news in France today. Led by the French vegetarian group L214, they gathered in front of the office of the Direction Générale de l'Alimentation, a branch of the Ministry of Agriculture, to call on the government to scrap a decree they claim effectively imposes meat consumption on six million French schoolchildren.

A law was passed on 3 October which obliges school canteens feeding more than 80 children to adhere to minimum nutritional requirements, setting in stone how much protein, iron, calcium and fresh fruit schoolchildren should be given.

Schools now have to provide meals which include a protein element with accompaniment, such as rice or vegetables, a dairy product (for example cheese or yoghurt) and either a starter or a pudding. The protein can be cheese but a dairy product is also obligatory as a separate element.

So while the new rules do not explicitly ban vegetarian meals, Brigitte Gothière of the vegetarian association L214 says they make it clear that the state believes all sources of protein should come from animal, not vegetable, products. On a 20-meal cycle, a minimum of four meals must include "quality meat" and four "quality fish," and on the other days, egg, cheese or "abats" (offal) should be the main dish. Isabelle Dudouet-Bercegeay, president of the Association Végétarienne de France, says: "It's a case of 'If you don't want your child to eat meat, don't use the canteen.'"

Vegetarian groups in France argue the decree could mean schools offering vegetarian meals are breaking the law, while they effectively make veganism at school impossible. In a statement protesting against the decree, L214 says: "The government has brought the law into school catering, imposing a model based on a high consumption of animal products and banning vegetarianism."

In response to the protests, Matthieu Grégory, food adviser to the minister, told le Parisien the decree fits in with national Nutrition Santé (nutrition and health) plans and offers a "balanced diet." He said: "Menus with a substitution can continue to exist if towns adhere to the decree. We will look at this on a case by case basis."

School meals in France are a very different affair to their British equivalent. French children are happy meat eaters and frequently sit down to a lunch of rabbit, veal, cassoulet or raclette with accompanying charcuterie. But most French school canteens are supplied by a local, central kitchen and many "maternelles" (pre-schools up to age six) and "élémentaires" (for ages six to 10) only offer one meal option each day, so on a day when meat is the main dish, say the groups, there is no room for a vegetarian option. Older children often have a self-service system, so could opt out of meat. Since this is likely to be the only protein on offer, though: "That leaves them with a nutritionally deficient meal," says Gothière.

With a culture and cuisine that is so deeply in love with meat in all its forms, avoiding eating it in France is a tricky business. There is a very small minority of non-meat eaters in the country – more than the 20 who demonstrated today, but still tiny. One million people, or 1.5% of the French population called themselves vegetarian in studies published in the late 1990s, although more recent estimates suggest that has grown to 2%. Dudouet-Bercegeay says: "I have been vegetarian for 23 years and it is getting easier, but there was a time when it was extremely difficult." I can concur. My husband's French grandmother, when faced with making me a lunch "sans viande" for the first time, said: "No problem, I'll cook chicken."