They were after, it turns out, his digital devices and the information stored on them. The search warrant, which Arnu has since posted online, indicates that the teams sought evidence that Arnu had violated U.S. laws against photographing military installations. Were they worried that he had pointed his camera too far inside Area 51, or did he possess even more sensitive information?

In the months since the search, Arnu says he’s been unable to determine what the FBI and Air Force were after, or whether they will ever charge him with a crime. The investigation, though, probes the balance between government opacity and openness, the desire to keep secrets in the interest of national security, and the value of transparency in a democracy. And if a case against Arnu goes forward, it could have troubling implications for what information is illegal to possess or make public.