An outspoken advocate for an Army private accused of funneling classified documents to Wikileaks filed suit Friday, claiming federal agents illegally seized confidential information from him at a Chicago airport.

David House, a founding member of The Bradley Manning Support Network, had his laptop, a thumb drive and video camera taken in November after two Department of Homeland Security agents detained and questioned him about Wikileaks and his association with Manning, according to the suit.

The items allegedly weren't returned to House for seven weeks. During that time, House's personal information as well as private documents related to the Manning network were copied and given to other federal agencies, according to the suit filed by the American Civil Liberties Union.

The actions violated House's free speech rights and Constitutional protections against unreasonable search and seizure, according to the suit, which asks the court to order the government to return or destroy any information taken from House's device.

The seizure of House's materials "will chill the association rights of the Bradley Manning Support Network" by exposing them to harassment, retribution or by stopping them from freely discussing political tactics, the suit alleges.

The suit was filed at U.S. District Court in Boston. It names the Department of Homeland Security, Customs and Border Protection and Immigration and Customs Enforcement agencies as defendants.

A Department of Homeland Security spokesman, Adam Fetcher, said Friday the department doesn't comment on pending litigation.

House, 24, called the case a "transpartisan issue" because the government is violating rights critical to all U.S. citizens.

"I don't think that our government should be treating lawful activists like suspects," he said. "That's very alarming to me."

Manning, a former intelligence analyst, is accused of leaking hundreds of thousands of documents to the anti-secrecy website WikiLeaks. The documents include Iraq and Afghanistan war logs, confidential State Department cables and a classified military video of a 2007 Apache helicopter attack in Iraq that killed a Reuters news photographer and his driver.

After Manning's arrest, House and others formed the support network to, among other things, "harness the outrage of viewers" of the military video, raise money for Manning's defense and support him during his imprisonment, according to the suit.

A motto on the group's website says, "Blowing the whistle on war crimes is not a crime."

House, a Cambridge, Mass., computer programmer, is one of the group's chief fundraisers and says he has visited Manning at the Marine Corps Base in Quantico, Va., where Manning is awaiting trial.

The suit claims House has been under intense federal scrutiny since he became involved in Manning's support network.

It says he's been questioned at home and work by investigators from the Department of Defense, Department of State and FBI. House was also placed on a watch list, and has subsequently been questioned each of the seven times he's returned to the U.S. after foreign travel, including being asked about his advocacy for Manning and political views, according to the suit.

House's electronic devices were taken Nov. 3 as he headed back to Boston through Chicago following a vacation in Mexico, and weren't returned until 49 days later, the suit said.

House said the government's seizure of his computer has had "a profound chilling effect" on the support network.

Many of Manning's advocates previously insisted on anonymity, and some supporters have been accused of treason, the suit said. Now they won't even give basic information, such as their email addresses, for fear of being discovered and targeted by the government, House said.

"It silenced people who were once very outspoken and it's caused a lot of donors to retreat," House said. "I think what we're seeing here is a systematic encroachment on the private rights of citizens by the U.S. government."