Suppose I approached you with a request. I want you to carry a small gadget that will automatically transmit your location to the police, allowing them to track your every movement 24 hours a day, 365 days a year. Chances are you would politely decline.
Too late. You already accepted.
That gadget, you see, is called a cell phone. For years, the cops may have been using it to keep close tabs on you without your knowledge, even if you have done nothing wrong.
They don't have to get a search warrant -- which would limit them to situations where they can show some reason to think you're breaking the law. All they have to do is tell a judge that the information is relevant to a criminal investigation and send a request to your service provider.
This does not appear to be an uncommon event. Al Gidari, an attorney for several service providers, told Newsweek they now get "thousands of these requests per month."
Oh, and the data are not limited to your movements today or in the future. The government can also see records of where you've been in the past. So if you got skittish and decided to stop packing a wireless communications device, your privacy would still be at risk.
You can be vulnerable even if the police have no particular interest in you. Michael Sussmann, another lawyer for service providers, said in 2006 that sometimes, "we get a subpoena for information on one person and then they want all the information on the persons calling or called by them."
These developments explain why a coalition of organizations and companies -- including Google, AT&T, the Competitive Enterprise Institute and the American Civil Liberties Union -- have joined in asking Congress to drag our privacy laws into the 21st century. They think search warrants should be required before law enforcement can demand this sort of electronic communications information.
You might assume unchecked government surveillance of innocent people went out of style when George W. Bush took his leave. But this is one of those instances that seem designed to show the futility of trying to change policy by changing the party in power. Barack Obama's Justice Department also insists it should have the authority to conduct such tracking without a warrant.
Some judges don't buy it. A couple of years ago, a federal court in Pennsylvania said the practice was at odds with both federal law and the Fourth Amendment to the Constitution, which forbids "unreasonable searches and seizures." Cell-phone location tracking, the judge concluded, invades the privacy Americans have a right to expect.
No kidding: It can reveal if someone is having an affair, visiting a gay bar, attending a militia meeting or tea party event, going to an abortion clinic, seeing a psychiatrist, getting treatment for substance abuse, worshiping at a mosque and any number of other activities some people would rather conceal from a government they do not fully trust.
Those on the other side think a warrant requirement would be unreasonable, since a cop doesn't need court permission to follow you down the street on a hunch. But Northwestern University law professor Albert Alschuler says, "There's a big difference between watching you all the time, everywhere you go, and watching you pass by."
Police departments will never have enough cops to physically tail you and millions of other people constantly. But the spread of cell phones makes it possible for law enforcement to conduct endless surveillance on a scale that is both vast and intimate.
Privacy protections can become meaningless if we don't adapt them to new inventions. Today, we take it for granted that the FBI can't listen to our phone conversations without a search warrant. But in 1928, the Supreme Court said the Fourth Amendment did not apply to anyone "who installs in his house a telephone instrument with connecting wires … to project his voice to those quite outside."
Not until 1967 did the court correct that blunder. It ruled that "the Fourth Amendment protects people, not places," including those things a person "seeks to preserve as private, even in an area accessible to the public."
Maybe it still does. Or maybe not.