An inmate at the Louisiana State Penitentiary claims he was thrown into lockdown because his mother posted an advertisement on the Internet in search of an attorney for him, a federal court suit alleges.

The suit, filed by the American Civil Liberties Union on behalf of Shannon Dale Cassels, claims that his free-speech rights and constitutional right to access the court system were violated by the state.

Cassels is serving a life sentence for second-degree murder.

Joe Cook, head of the ACLU in Louisiana, said the case began in August 2001 when Cassels, who was working in the fields in Angola, suffered an allergic reaction and requested medical treatment that was denied. As a result, he refused to work and was disciplined, the suit said.

The next month, Cassels called his mother about what had happened, and she posted an dvertisement on the Internet asking for legal assistance for her son. The ad was noticed by prison officials about a year later and Cassels was placed in disciplinary lockdown, the suit said.

The suit, filed in U.S. District Court in Baton Rouge, said Cassels was disciplined under prison rules prohibiting the spreading of rumors and any action "that may impair or threaten the security or stability of the unit or well-being of an employee, visitor, guest inmate or their families."

The suit also alleges that after his release from lockdown, Cassels' mail between him and his attorneys was improperly opened by prison officials.

Cassels is seeking unspecified damages.

The disciplinary rules are so vague that they can be arbitrarily applied by prison officials for any reason in violation of due-process rights guaranteed by the U.S. Constitution, Cook said.