The police presence and officers’ response is determined on a case-by-case basis, law enforcement officials said. Those interviewed said they support protesters’ First Amendment rights to free speech and assembly, but that demonstrations shouldn’t evolve into breaking the law or putting themselves or others in danger.

One of the books is alleged to have hit a car, leading to the felony crime of throwing an object onto the freeway with the intent to cause great bodily injury during an immigration protest.