PARIS, Feb. 27 - More than 200 political demonstrators defied a police ban here on Thursday, scurrying across Boulevard St.-Germain and under the sycamore trees of Place Maubert to engage in their forbidden action: eating "pig soup" in public.

With steaming bowls of the fragrant broth soon passing through the crowd, Odile Bonnivard, a short-haired secretary turned far-right firebrand, climbed atop a dark sedan with a megaphone in hand and led the crowd in a raucous chant: "We are all pig eaters! We are all pig eaters!"

Identity soup, as the broth has come to be called, is one of the stranger manifestations of a growing grass-roots backlash against the multiculturalism that has spread through Europe over the past 20 years. People are increasingly challenging the care taken in Nazi-chastened Europe, and in France in particular, to avoid the sort of racial or religious insults that led to widespread protests in the Muslim world this month after wide publication of cartoons considered offensive to the Prophet Muhammad.

The movement began in the winter of 2003 when Ms. Bonnivard, a member of a small far-right nationalist movement called the Identity Bloc, began serving hot soup to the homeless. At first, she said, the group used pork simply because it was an inexpensive traditional ingredient for hearty French soup. But after the political significance of serving pork dawned on them and others, it quickly became the focus of their work.