The DHS has responded to a Freedom of Information Act request filed by the ACLU asking when and how it decides whose laptop to search at the border. It explained its legal rationale for conducting these searches with a blank page:
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."
More excellence from "the most transparent administration in American history." Also, the DHS rejected claims that it should limit searches to situations where it had reasonable grounds for suspicion, because then they would have to explain their suspicion:
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.
Feds say they can search your laptop at the border but won’t say why [Cyrus Farivar/Ars Technica]