When I was a Business Agent it was mandatory that we become familiar with the Pruneyard decision, which allows for informational picketing on private property. So the First Amendment of the Constitution finally went beyond the private property line. When the owners of the business we were picketing called the law, we had copies of the decision to give the cops.
Now all that will change and our rights as citizens once again are limited to publicly owned property.
What was the Pruneyard Decision? Ever since 1975, California law establishes tough standards for courts to issue injunctions against demonstrators in labor disputes. The Supreme Court upheld that law in 1980.