Under the Fourth Amendment to the United States Constitution, Americans are generally protected from unreasonable searches and seizures by government agents. But we generally have less privacy at the border—usually when entering the United States from abroad.

At present, border agents do not have to provide a warrant or have reasonable suspicion to search your laptop—they essentially just need a hunch. For some time now, civil liberties groups have been pressing to change that policy. At the very least, these groups would like to compel the government to explain its legal rationale.

Back in February 2013, the Office for Civil Rights and Civil Liberties at the Department of Homeland Security (DHS) released an executive summary (PDF) of its findings to justify warrantless border searches of laptops. However, that summary did not include any substantial analysis of the reasoning the government provides.

On Wednesday, though, in response to a Freedom of Information Act request filed by the American Civil Liberties Union (ACLU), the DHS released (PDF) its complete December 2011 Civil Rights/Civil Liberties Impact Assessment.

The assessment first counters by noting:

The issue is an important one even though it affects only a very small proportion of the many millions of travelers who enter the United States each month. The table below summarizes the relevant statistics; as it shows, only a few hundred people each month are subjected to any kind of electronic device search (which vary in their comprehensiveness), and of that number, only a small minority have their electronic devices detained for any length of time.

According to the government’s own figures, there were only 302 travelers subject to an average of electronic device searches monthly in 2009 and 383 (monthly average) in 2010. Still, that raises the question: what is the government’s constitutionally based reasoning for such searches? Frankly, we don’t know. A lot of it is redacted.

On Page 18 of the 52-page document under the section entitled “First Amendment,” several paragraphs are completely blacked out. They simply end with the sentence: “The laptop border searches in the [Immigration and Customs Enforcement] and [Customs and Border Protection] do not violate travelers’ First Amendment rights as defined by the courts."

Because we say so

The DHS also says that it definitely can’t change its policies to be “suspicion-based,” as that would be “operationally harmful.” Why?

First, commonplace decisions to search electronic devices might be opened to litigation challenging the reasons for the search. In addition to interfering with a carefully constructed border security system, the litigation could directly undermine national security by requiring the government to produce sensitive investigative and national security information to justify some of the most critical searches. Even a policy change entirely unenforceable by courts might be problematic; we have been presented with some noteworthy CBP and ICE success stories based on hard-to-articulate intuitions or hunches based on officer experience and judgment. Under a reasonable suspicion requirement, officers might hesitate to search an individual's device without the presence of articulable factors capable of being formally defended, despite having an intuition or hunch based on experience that justified a search.

However, the government did provide a pointed response to arguments that ICE and CBP should revert to a 1986 policy. That legislation allowed agents to “briefly peruse” a traveler’s possessions to determine if there was probable cause or a reasonable suspicion for a further seizure.

This approach is not tenable in the context of modern electronic devices. Gigabytes of information may be stored in password-protected files, encrypted portions of hard drives, or in a manner intended to obscure information from observation. An on-the-spot perusal of electronic devices following the procedures established in 1986 could well result in a delay of days or weeks; even a cursory examination of the contents of a laptop might require a team of officers to spend days or weeks skimming the voluminous contents of the device. At the same time, a firm time limit for completing a search risks allowing a wrongdoer to "run out the clock" by encrypting and password-protecting his device, or traveling with voluminous amounts of documents, or other measures to make the search very time consuming.

Not surprisingly, the ACLU takes issue with this line of reasoning. In a blog post on Wednesday, Brian Hauss, a legal fellow at the ACLU’s Speech, Privacy, and Technology Project, wrote: