I'M A LIFELONG Philadelphian who's fortunate to earn a living doing what I love: giving guided tours of our historic city.

But if a law recently signed by Mayor Nutter goes into effect, I will soon be forced to get the government's permission to speak - and be subject to hundreds of dollars in fines for, amazingly, talking without a license.

For more than a hundred years, my family has lived in the heart of Philadelphia. My mother's side of the family came here in the 1800s, and my father's ancestors are believed to have fought in the Civil War. It's often said that you know you're from Philadelphia when your entire family lives within a five-block radius. In my case, it's true.

Three years ago, I decided to look for a side job and realized I had a flair for giving tours. I've been doing it ever since.

Being a guide allows me to combine three of my passions: history, performance and a love of Philadelphia. I work for Constitutional Walking Tours, taking my customers through the historic district and bringing to life the deep history of such staples as Independence Hall, the Betsy Ross House, Old Saint Mary's and the Liberty Bell.

This spring, however, the mayor decided to create a tour-guide bureaucracy, effective this October, which will make it illegal for people like me to continue to earn an honest living doing what we love unless we first obtain a government-issued license and pass an arbitrary test.

Only then may we continue to speak out about such local hallmarks as the Declaration of Independence.

But our history is diverse and no test could possibly capture everything that Philadelphia has to offer. Will the city be hiring expert historians to police the guides? How will they know which of the countless anecdotes told every day are true?

I also guide three other distinctly different tours. In the evening, I run the Spirit of '76 Ghost Tours, where - besides historical facts - we wade through haunted folklore like the ghosts of Independence Hall.

One scary story alleges that, in the 1990s, security guards watching a monitor saw someone standing in a room on the second floor. A guard walked up into the room and reported on his walkie-talkie that no one was there. To his shock, he was told that the man appeared to be standing right in front of him.

Will such entertaining tales be allowed to be shared only after completion of a government-mandated ghost test?

A number of loyalists lived in Philadelphia during the American Revolution. Ben Franklin owned slaves here and, in fact, people have found sections in his newspaper that advertised slaves.

Those answering the ads were asked to see the publisher, implying that Franklin may have been involved in selling slaves. What if officials don't want us to discuss the fact that the Cradle of Liberty had loyalists and and a favorite son may have been involved in slavery?

But the government should never be able to control what we say, particularly in the very place where our most fundamental freedoms were first articulated.

Several decades before the Declaration of Independence was signed in Independence Hall, our ancestors enjoyed a state constitution given to us by William Penn that secured cherished liberties. At one time, there were as many as eight newspapers in Philadelphia - and everyone had the opportunity to print what they saw fit. The freedom to speak has, from the very beginning, been at the very foundation of our liberty-rich city.

We must not allow this freedom to be curtailed.

THAT'S WHY I've teamed up with the Institute for Justice, a national public-interest law firm with a history of protecting the First Amendment and the freedom to earn an honest living. Along with two other tour guides, we are filing suit today to vindicate the rights of all Philadelphians and keep them from being subject to unconstitutional attacks.

It is the right of every American to challenge laws that are unfair and wrong. As a matter of fact, that was what the signing of the Declaration of Independence in Philadelphia - and the birth of our nation - was all about. *

Mike Tait is a Philadelphia tour guide who is filing a lawsuit today against the city to secure his constitutional rights.