Free speech ain't cheap. It was paid for with the blood of patriots who died so that I could call a prominent politician a baggy-lipped, biffle-backed bozo without fear of legal reprisal.

This is not something that I take lightly. Those who defend the right of free speech are my brothers in arms - up to a point.

That point may have been exceeded yesterday by a fine young lawyer named Robert McNamara from an organization of constitutional zealots called the Institute for Justice. The institute claims a long string of successes in its campaigns to get government off the backs of small businesses.

When three states tried to force African hair braiders to be licensed cosmetologists, the institute was there. When a New Mexico law prohibited anyone not licensed by the state to call himself an interior designer, the institute was there.

Even now, they are in pitched battle with the state of Louisiana over laws requiring anyone who sells two or more kinds of flowers in a single bunch to be licensed by the state and have their flower arrangements judged by a panel of "industry experts."

It's good to know that there are still young people in America who rise up in righteous indignation over these abuses of government power.

But the institute and I part company on their campaign to strike down a law signed by Mayor Nutter in April to require Center City tour-guide operators to be certified, licensed and knowledgeable.

Councilwoman Blondell Reynolds Brown's bill requires the guides to pass a test on Philadelphia history and geography before they can lead tours in the areas between the rivers and from South Street to Vine.

Is that so much to ask? Millions of visitors drop $10 billion here each year. Many of them learn Philadelphia history from horse-carriage drivers and tour-bus guides who can't tell you which two countries fought in the Spanish-American war.

But the institute is standing up for their God-given right to dispense disinformation. They had planned to file suit in federal court here on behalf of tour guides Michael Tait, Joshua Silver and Ann Boulais, and they base their claim on the right of free speech.

The defendants, the suit claims, are "committed to protecting their right to speak freely in the birthplace of the Constitution and are unwilling to submit to a program under which the government will have authority to determine who may or may not speak."

Dem's fightin' words! But we lovers of the First Amendment also know that there are limits. A politician's prominence may protect me from a libel suit. But I still can't stand up in a crowded theater and yell "yo biffleback, your seat's on fire."

A woman in spiked heels and fishnet stockings can't walk up to a car and say, "Hey, Joe, wanna give it a go?" even though she, too. is arguably working in the city's tourism industry.

These may not be the best examples but you get my point: There are rules even for rights.

But lawyers for the plaintiffs say their clients face "continued and irreparable harm," "prior restraint" of speech and "unchecked discretion" by the administrative agency that would oversee the law.

That last one raises a valid issue. The bill imposes fines and suspensions against guides who misinform their clients. You've got to wonder what agency in this town is going to deploy inspectors to check out what tourists are being told.

How do they distinguish between an honest error and malicious misinformation? Who is going to devise the test and how many of us could pass?

McNamara also raised a valid question about why the city couldn't impose voluntary certification and just give official badges to the guides who passed.

I couldn't reach Reynolds-Brown for comment on these issues yesterday. She may have been exercising her constitutional right to ignore me. *