The right to "peaceable assembly" is a fundamental First Amendment protection that allows citizens to gather to publically air their grievances. Freedom of assembly is what empowered the nonviolent civil rights movement of the 1960s to bring the injustices of segregation to national attention. So why is it that we often see scenes on TV of police arresting peaceful protesters or employing tear gas to disperse a crowd?
First of all, protests that occur on private property are unprotected by the First Amendment. A private property owner reserves to right to kick out individuals or groups for any reason [source: First Amendment Center]. If protesters refuse to vacate private property, they can be arrested for trespassing.
But what about protests in public streets and town squares? The Supreme Court has found that cities and municipalities have the right to restrict the time, place and manner of public demonstrations. These restrictions on the freedom of assembly are constitutional as long as they are "content-neutral," meaning the same rules are applied to everyone — from Girl Scouts to Neo Nazis — regardless of the content of a group's message [source: Goyette].
Most cities require permits for parades, protest marches and picket lines. They also have laws against blocking traffic and making excessive noise after certain hours. Groups that break those laws can be forcibly dispersed or arrested, even if their speech is otherwise protected.