"When Government seeks to use its full power, including the criminal law, to command where a person may get his or her information or what distrusted source he or she may not hear, it uses censorship to control thought. This is unlawful. The First Amendment confirms the freedom to think for ourselves."

Those words, penned by U.S. Supreme Court Justice Anthony M. Kennedy, were core to the court's 5-4 Citizens United ruling in 2010, which overturned the 2002 McCain-Feingold campaign finance law. That decision set off a firestorm in liberal land.

As the storm raged this year, the California Legislature passed a resolution calling on Congress and states to ratify a constitutional amendment to overturn the big bench decision. Five other states have passed similar measures.

This week, San Francisco joined in by placing an anti-Citizens United advisory measure on the city ballot.

It is instructive to note that though Citizens United ended restrictions on independent political spending by corporations and labor unions, the San Francisco and California measures seek to curb only corporate speech. No mention of labor.

The San Francisco measure, authored by Supervisor John Avalos, declares it city policy to repeal "corporate personhood" and "opposes artificial corporate rights and giving corporations the same rights entitled to human beings." (By the way, corporations don't have the same rights as people; they can't vote, and they can't run for office.)

Speaking to the board before it unanimously passed the measure Tuesday, Avalos explained that the ruling allowed independent expenditure campaigns to air "commercials that can say just about anything on our televisions about candidates and about issues."

That's right, supervisor; it's called free speech.

When speech is inaccurate, the proper response is not to try to ban it but to argue against it — that is, to trust voters to decide for themselves.

Campaign finance attorney Allison Hayward is appalled that California's progressive movement, which allegedly is premised on pushing back against power, has chosen to oppose a court decision that is "the most simplistic extension of free speech." As she sees it, "the whole notion of liberty as expression has just blown up."

Be it noted that political organizations qualify as corporations under the ruling. As the American Civil Liberties Union likes to point out, Citizens United applies not only to General Motors and Microsoft but also to nonprofit corporations, such as Planned Parenthood and the National Rifle Association.

"Our system of free expression is built on the premise that the people get to decide what speech they want to hear," an ACLU paper argued in March. "It is not the role of the government to make that decision for them."

The worst part: Once again, the San Francisco Board of Supervisors is oblivious to its tendency to censor unwanted opinion. Sure, the supes love free speech — right up until they realize that moderates or conservatives also get to use it.