NEW YORK, Sept 13 (Reuters) - An unusual lawsuit brought by a Louisiana group that represents death row prisoners is pitting two bedrock legal principles against each other: free speech and attorney-client privilege.

The Louisiana Capital Assistance Center, a New Orleans-based anti-death penalty law office, is suing Alexandria Marzano-Lesnevich, a graduate of Harvard Law School who interned at the center in the summer of 2003. During her stint with the center, Marzano-Lesnevich worked on a number of cases and met with center client Ricky Langley, a convicted pedophile who was later convicted in the 1992 killing of a six-year-old boy in Louisiana.

Marzano-Lesnevich has since pursued a career as a writer, and in 2010 published an essay in a literary journal that included details from Langley's confession and his actions on the day of the child's death. Marzano-Lesnevich is now working on a book that details her own childhood experiences as the victim of sexual abuse and again references details of the Langley case.

The center complained about the essay when it was published, and once it learned Marzano-Lesnevich was writing a book, sought an injunction to prevent her from disclosing information it found objectionable. That suit was filed in July in Louisiana state court.

Typically in attorney-client privilege cases, it is the client who asserts a breach of confidentiality. But Langley has not filed such a claim. Instead the center has taken up the case to protect him and clients like him, experts said. To make the argument, the center has alleged that Marzano-Lesnevich had an oral employment contract with the center and that, by publishing details from the Langley case, she violated that contract and the fiduciary duty owed the center.

BORDERING ON THE ABSURD

On Aug. 24, Marzano-Lesnevich moved to dismiss the injunction request on First Amendment grounds and removed the case to federal court. In her motion, Marzano-Lesnevich also disputed the idea that the information in her essay and book is privileged. She argued that an injunction would constitute an unconstitutional prior restraint and that the "breadth" of what the center wants suppressed "borders on the absurd."

It is unusual for a court to be forced to weigh attorney-client privilege claims versus First Amendment rights in this way. The most memorable recent instance was more than 20 years ago -- prior to the trial of former Panamanian dictator Manuel Noriega for drug trafficking and money laundering. In November 1990, a U.S. trial judge ordered CNN to temporarily refrain from broadcasting tapes that showed Noriega speaking with his lawyer until the judge could review the tapes. The Eleventh Circuit Court of Appeals upheld the prior restraint order, but CNN broadcast the tapes anyway. A district court later held, in part, that a permanent injunction would be useless since the information had already been broadcast.

"Prior restraints on speech are, as the Supreme Court observed in 1976, 'the most serious and the least tolerable infringements on First Amendment rights,'" said First Amendment expert Floyd Abrams of Cahill, Gordon & Reindel. But striking a balance may be difficult for a court when a defendant's right to a fair trial is at stake -- as was thought to be the case with Noriega, Abrams said. Simply put, courts usually don't like to limit what people can say before they have a chance to say it.

CAN'T UNRING THAT BELL

Typically, courts allow publication and then deal with the damages later. "When it comes to client confidences, once you let it out there you can't unring that bell. And that will be the tension for the judges," said Laurin Mills, a partner in LeClaire Ryan who represents media organizations.

One possible weakness in the center's case against Marzano-Lesnevich, experts said, is that the complaint does not specifically describe the information it wants kept private. Instead, the group asked that Marzano-Lesnevich be prohibited from publishing any attorney-client communications, material she worked on, and confidential information she learned while interning at the center. It also asked the court to suppress information relating to her representation of clients that could disadvantage or prejudice those clients.

The center is making an "unfocused blunderbuss request that it's going to be very hard to grant," said Bernard Burk, an assistant professor at the University of North Carolina law school, who specializes in professional responsibility.

In documents filed under seal, the center discusses specific passages in Marzano-Lesnevich's essays that it objects to, but states that the injunction request is "narrowly tailored."

DEFENDING CASES EFFECTIVELY

A lawyer for the center declined to comment, but legal ethics experts said it is trying to protect both Langley and future clients who might worry their confidences could be revealed, which in turn could affect a lawyer's ability to defend a case effectively.

On Friday, the center filed a response to Marzano-Lesnevich's motion to dismiss, stating that the case turned on Marzano-Lesnevich's obligtions to the center and her clients, not free speech. The First Amendment "is not implicated when a person like Ms. Marzano Lesnevich assumes a position of trust and then breaches it for her own self-interest." The Center cited Supreme Court precedent to argue that breaches of confidentiality agreements and fiduciary duty are not protected by free speech principles.

In her reply filed Tuesday, Marzano-Lesnevich maintained she had neither a contract with the center nor a legal duty to keep her work at the center confidential.

The case is Louisiana Crisis Assistance Center v. Marzano-Lesnevich, U.S. District Court for the Eastern District of Louisiana, No. 11-02102.

For the Center: Harry Hardin, Mark Cunningham and Christopher Cazenave of Jones, Walker, Waechter, Poitevent, Carrere & Denegre.

For Marzano-Lesnevich: Loretta Mince and Alysson Mills of Fishman Haygood Phelps Walmsley Willis & Swanson.

(Reporting by Erin Geiger Smith)