EFF: Secret Court Orders Aren’t Blank Checks for General Electronic Searches by Mark Rumhold:
Imagine this: the government, for reasons you don’t know, thinks you’re a spy. You go on vacation and, while you’re away, government agents secretly enter your home, search it, make copies of all your electronic devices, and leave. Those agents then turn those devices upside down, looking through decades worth of your files, photos, and online activity saved on your devices. They don’t find any evidence that you’re a spy, but they find something else—evidence of another, totally unrelated crime. You’re arrested, charged, and ultimately convicted, yet you’re never allowed to see what prompted the agents to think you were a spy in the first place.