Did you read what the actual ruling held? This wasn't a 1st Amendment case.
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In American constitutional law, this case established two important rules:
* under the California Constitution, individuals may peacefully exercise their right to free speech in parts of private shopping centers regularly held open to the public, subject to reasonable regulations adopted by the shopping centers
* under the U.S. Constitution, states can provide their citizens with broader rights in their constitutions than under the federal Constitution, so long as those rights do not infringe on any federal constitutional rights
This holding was possible because California's constitution contains an affirmative right of free speech which has been liberally construed by the Supreme Court of California, while the federal constitution's First Amendment contains only a negative command to Congress to not abridge the freedom of speech. This distinction was significant because the U.S. Supreme Court had already held that under the federal First Amendment, there was no implied right of free speech within a private shopping center.
It's not that simple.