The group building a vast Islamic mosque and social center in Roxbury has subpoenaed a local radio talk station after one of its prominent hosts, Michael Graham, discussed the project on the air.

A lawyer for the Islamic Society of Boston said the subpoena is part of routine evidence gathering for its defamation case against The Boston Herald, WFXT-TV (Fox 25) and advocacy groups that have questioned the mosque, including the David Project, a Jewish group.

Some civil liberties lawyers who reviewed the subpoena, however, expressed concern that it goes too far and could chill free expression.

ISB attorney Howard Cooper said “the appearance for the lawyer of the David Project on the Graham show is directly relevant to the issues before the court in the pending litigation, and this is why a subpoena has been issued simply asking for copies of the broadcast.”

But after reviewing the subpoena, attorney Harvey Silverglate, a Cambridge civil liberties specialist, described it as “extraordinary.” He noted that it also asks for materials used by Graham to support his remarks about the ISB, documents related to David Project lawyer Jeffrey Robbins’ appearance on the show and communications between Graham and other defendants or attorneys involved in the ISB defamation suit.

“Courts have to take seriously their obligation, their duty to protect the First Amendment, because civil litigation can be overwhelming and can really easily turn into harassment,” Silverglate said...

...North Carolina attorney W. Andrew Copenhaver, who is not involved in the defamation suit, said if he was defending WTTK in this matter he would argue the subpoena is a “fishing expedition.”

“They are trying to curtail legitimate public discussion on this matter,” said Copenhaver, who was referring to legal strategy. “They are going to try to punish people for talking about them.”...