Nina De Chiffre, 20, was photographed kissing the helmeted riot officer at a demonstration against a new high-speed train line between Italy and France last month.
The kiss was initially seen as a gesture of peace in the often violent protests. However, Ms De Chiffre later said on Facebook that she intended to mock the police, whom she called "disgusting pigs".
The police union said it had filed a criminal complaint. "If it was a policeman who kissed a demonstrator, the Third World War would break out," said Franco Maccari, leader of the union.
Comment: Oh really? If police at protests started kissing demonstrators the police would join the protestors and the psychopaths in power would be in BIG trouble!
"Sexual violence".....what a laugh. The ones accusing the young woman of this are most likely a bunch of men who can't stand the fact that a woman stood against them.