So, the FBI is lately using "national security letters", issued on its own initiative, without any judicial review, to get access to, well, pretty much anything they want to see. One known instance of this is a series of letters that requested information on just about every tourism-related transaction (hotels, rental cars, etc.), in Las Vegas in December, 2003. Judges who have seen the justification for these requests report that they are frequently issued on vague suspicion; one judge finally received a classified briefing and reported that it still contained "nothing specific". And those asked to turn over information on others are also forbidden to disclose the requests to anybody.

In this, we can see how punctiliously the government does what it needs within Constitutional limits on its power. The Fourth Amendment reads:

The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.

Well, peoples' papers and effects aren't being seized --- just copies of these things that other people might happen to have. So, no problem there. But even if you think there was one, and you're troubled by the lack of probable cause, or specificity in describing the places or things to be seized, be of good cheer. The Constition says "no Warrants shall issue", and these aren't warrants. They're National Security Letters. So of course, that's different.

Who knew that living within constitutional restraints on your power could be this easy?