How fragile a thing, law.

Not long ago, the notion that Americans could be seized off the streets, arrested, and jailed without probable cause might have seemed laughable. The power to incarcerate on mere suspicion or executive say-so belonged to dictatorships. "We allow our police to make arrests only on 'probable cause,'" we used to be told; "[a]rresting a person on suspicion, like arresting a person for investigation, is foreign to our system."

But in 2002, the President of the United States claimed and exercised the power to designate an individual, including an American citizen seized on American soil, an "unlawful enemy combatant"—and to imprison him on that basis, without probable cause and with limited if any judicial review.

Not long ago, it was possible to believe that the government could intercept Americans' telephone calls only with probable cause and, absent exigent circumstances, judicial authorization. As late as 2004, the President declared: "Now, by the way, any time you hear the United States Government talking about wiretap, it requires—a wiretap requires a court order. Nothing has changed, by the way. When we're talking about chasing down terrorists, we're talking about getting a court order before we do so. It's important for our fellow citizens to understand, when you think Patriot Act, constitutional guarantees are in place when it comes to doing what is necessary to protect our homeland, because we value the Constitution."

These statements, it turned out, were not true...