Updated

Federal attorneys on Monday jumped into a court battle over the construction of a Tennessee mosque by offering legal proof that Islam is a recognized religion entitled to constitutional protection.

U.S. Attorney Jerry E. Martin of Nashville said his office would not sit by while mosque opponents raise questions in court about whether Islam is a recognized religion. Martin said in a statement that to suggest otherwise "is quite simply ridiculous."

Martin's office filed a brief saying as much in a state lawsuit brought by mosque opponents against Rutherford County for granting permission for construction of the building.

Mosque opponents are challenging whether the county acted properly in granting the construction permit. Their complaint claims that the county failed to determine whether the Islamic Center of Murfreesboro is entitled to protection under the First Amendment. They have also claimed that the county violated the state's Open Meetings law in the approval process.

Martin said his office was not intervening in the lawsuit itself to take sides, but attorneys felt the need to weigh in on issues raised during three days of testimony in Rutherford County Chancery Court.

"Plaintiffs' implication that Islam is not a recognized religion by the United States is wrong and is not supported by any authority whatsoever," he said. "The right to assemble and worship as you please was literally the genesis of this country."

Martin said during the testimony, a county official was questioned on whether Islam was a federally recognized religion.

"All three branches of the government have repeatedly recognized Islam as a religion," he said.

Kathleen Bergin, a professor of law at South Texas College of Law in Houston, said the filing is "part of a larger effort by the Department of Justice to curb post 9/11 backlash against Islam."

She said the government would be interested in this particular case because federal statutes prohibiting religious discrimination would come into play if the decision of the county to approve the construction at the mosque was overturned.

He also noted that Congress enacted the Religious Land Use and Institutionalized Persons Act in 2000, which specifically forbids local governments from using land regulations to unfairly prevent people from building churches, synagogues, mosques or other places of worship.

Martin said his office and the Justice Department's Civil Rights Division have been monitoring the case and doing outreach with Muslims in the area.

Although Martin said the lawsuit was a local matter, he added that the Justice Department supports the county's decision to approve the site plans earlier this year. He said if the county had followed the position proposed by the opponents, the county would have likely been in violation of the 2000 law.

The lawsuit asking a judge to stop the construction is ongoing.

The Justice Department has been investigating a handful of anti-Muslim incidents in four states, including a suspicious fire that damaged construction equipment at the site of the future mosque. Martin said no determination had been made on whether it was a hate crime, but a reward has been offered for information regarding the fire and Martin encouraged people to come forward.

Bergin said the fire is another reason why the federal government would want to get involved because it raises the issue of hate crimes against Muslims, an area of focused enforcement by the DOJ's Civil Rights division.

"You have this on-the-ground fervor of anti-Islamic backlash and I think the federal government is trying to temper that," she said.

Many have weighed in on a controversial mosque planned for near ground zero in New York City. The sides have gotten so heated that the wife of the imam planning the Islamic community center said her husband has received death threats.

Critics say the site of mass murder by Islamic extremists is no place for an Islamic institution, while supporters of the center say religious freedom should be protected.

The federal attorney's office in Nashville also prosecuted three men for 2008 firebombing of another mosque in Columbia, Tenn. All three pleaded guilty and were sentenced to prison.