One of the more extreme government abuses of the post-9/11 era targets U.S. citizens re-entering their own country, and it has received far too little attention. With no oversight or legal framework whatsoever, the Department of Homeland Security routinely singles out individuals who are suspected of no crimes, detains them and questions them at the airport, often for hours, when they return to the U.S. after an international trip, and then copies and even seizes their electronic devices (laptops, cameras, cellphones) and other papers (notebooks, journals, credit card receipts), forever storing their contents in government files. No search warrant is needed for any of this. No oversight exists. And there are no apparent constraints on what the U.S. Government can do with regard to whom it decides to target or why.

In an age of international travel — where large numbers of citizens, especially those involved in sensitive journalism and activism, frequently travel outside the country — this power renders the protections of the Fourth Amendment entirely illusory. By virtue of that amendment, if the government wants to search and seize the papers and effects of someone on U.S. soil, it must (with some exceptions) first convince a court that there is probable cause to believe that the objects to be searched relate to criminal activity and a search warrant must be obtained. But now, none of those obstacles — ones at the very heart of the design of the Constitution — hinders the U.S. government: now, they can just wait until you leave the country, and then, at will, search, seize and copy all of your electronic files on your return. That includes your emails, the websites you’ve visited, the online conversations you’ve had, the identities of those with whom you’ve communicated, your cell phone contacts, your credit card receipts, film you’ve taken, drafts of documents you’re writing, and anything else that you store electronically: which, these days, when it comes to privacy, means basically everything of worth.

This government abuse has received some recent attention in the context of WikiLeaks. Over the past couple of years, any American remotely associated with that group — or even those who have advocated on behalf of Bradley Manning — have been detained at the airport and had their laptops, cellphones and cameras seized: sometimes for months, sometimes forever. But this practice usually targets people having nothing to do with WikiLeaks.

A 2011 FOIA request from the ACLU revealed that just in the 18-month period beginning October 1, 2008, more than 6,600 people — roughly half of whom were American citizens — were subjected to electronic device searches at the border by DHS, all without a search warrant. Typifying the target of these invasive searches is Pascal Abidor, a 26-year-old dual French-American citizen and an Islamic Studies Ph.D. student who was traveling from Montreal to New York on an Amtrak train in 2011 when he was stopped at the border, questioned by DHS agents, handcuffed, taken off the train and kept in a holding cell for several hours before being released without charges; those DHS agents seized his laptop and returned it 11 days later when, the ACLU explains, “there was evidence that many of his personal files, including research, photos and chats with his girlfriend, had been searched.” That’s just one case of thousands, all without any oversight, transparency, legal checks, or any demonstration of wrongdoing.

But the case of Laura Poitras, an Oscar-and Emmy-nominated filmmaker and intrepid journalist, is perhaps the most extreme. In 2004 and 2005, Poitras spent many months in Iraq filming a documentary that, as The New York Times put it in its review, “exposed the emotional toll of occupation on Iraqis and American soldiers alike.”

The NYT feature on “The Oath” stated that, along with “My Country, My Country,” Poitras has produced ”two of the most searching documentaries of the post-9/11 era, on-the-ground chronicles that are sensitive to both the political and the human consequences of American foreign policy.” At the 2010 Sundance film festival, “The Oath” won the award for Best Cinematography.

Poitras’ intent all along with two documentaries was to produce a trilogy of War on Terror films, and she is currently at work on the third installment. As Poitras described it to me, this next film will examine the way in which The War on Terror has been imported onto U.S. soil, with a focus on the U.S. Government’s increasing powers of domestic surveillance, its expanding covert domestic NSA activities (including construction of a massive new NSA facility in Bluffdale, Utah), its attacks on whistleblowers, and the movement to foster government transparency and to safeguard Internet anonymity. In sum, Poitras produces some of the best, bravest and most important filmmaking and journalism of the past decade, often exposing truths that are adverse to U.S. government policy, concerning the most sensitive and consequential matters (a 2004 film she produced for PBS on gentrification of an Ohio town won the Peabody Award and was nominated for an Emmy).

But Poitras’ work has been hampered, and continues to be hampered, by the constant harassment, invasive searches, and intimidation tactics to which she is routinely subjected whenever she re-enters her own country. Since the 2006 release of “My Country, My Country,” Poitras has left and re-entered the U.S. roughly 40 times. Virtually every time during that six-year-period that she has returned to the U.S., her plane has been met by DHS agents who stand at the airplane door or tarmac and inspect the passports of every de-planing passenger until they find her (on the handful of occasions where they did not meet her at the plane, agents were called when she arrived at immigration). Each time, they detain her, and then interrogate her at length about where she went and with whom she met or spoke. They have exhibited a particular interest in finding out for whom she works.

She has had her laptop, camera and cellphone seized, and not returned for weeks, with the contents presumably copied. On several occasions, her reporter’s notebooks were seized and their contents copied, even as she objected that doing so would invade her journalist-source relationship. Her credit cards and receipts have been copied on numerous occasions. In many instances, DHS agents also detain and interrogate her in the foreign airport before her return, on one trip telling her that she would be barred from boarding her flight back home, only to let her board at the last minute.

When she arrived at JFK Airport on Thanksgiving weekend of 2010, she was told by one DHS agent — after she asserted her privileges as a journalist to refuse to answer questions about the individuals with whom she met on her trip — that he “finds it very suspicious that you’re not willing to help your country by answering our questions.” They sometimes keep her detained for three to four hours (all while telling her that she will be released more quickly if she answers all their questions and consents to full searches).

Poitras is now forced to take extreme steps — ones that hamper her ability to do her work — to ensure that she can engage in her journalism and produce her films without the U.S. Government intruding into everything she is doing. She now avoids traveling with any electronic devices. She uses alternative methods to deliver the most sensitive parts of her work — raw film and interview notes — to secure locations. She spends substantial time and resources protecting her computers with encryption and password defenses. Especially when she is in the U.S., she avoids talking on the phone about her work, particularly to sources. And she simply will not edit her films at her home out of fear — obviously well-grounded — that government agents will attempt to search and seize the raw footage.

That’s the climate of fear created by the U.S. Government for an incredibly accomplished journalist and filmmaker who has never been accused, let alone convicted, of any wrongdoing whatsoever. Indeed, documents obtained from a FOIA request show that DHS has repeatedly concluded that nothing incriminating was found from its border searches and interrogations of Poitras. Nonetheless, these abuses not only continue, but escalate, after six years of constant harassment.