The use of violence and violent protest
Violence - behaviour involving physical force, with the intention of hurting or damaging, or killing someone and something
Examples:
The London riots (2011) sparked by the killing of Mark Duggan, a 29 year old black man who was shot dead by the police.
The Tiananment Square Protests, Beijing, China (1989). Pro-democracy demonstrators, primarily students, gathered in Tiananment square to call for political reforms and greater freedoms.
UK law legal rights of non-violent protest:
petitions
free speech
strike
protest with signs