According to a slew of federal court rulings, police can use hidden tracking devices to monitor the public movements of a person or vehicle without bothering with a court order, since these devices don't violate any "reasonable expectation of privacy." But the sponsors of a bill making its way through the Georgia General Assembly think these GPS trackers do violate a privacy interest worth protecting—at least when they're used by private citizens.

House Bill 16, sponsored by State Rep. Kevin Levitas, would make it a crime to "use an electronic tracking device to determine the location or movement of another person without such other person's consent," with a few notable exceptions. "I think you or I need to be able to go to the shopping center, get a carton of eggs, and not have to check under our car to see if someone placed a tracking device," Levitas explained to a local news station. "I think the legislation's good so any John Doe person can't walk into a store, buy a GPS and throw it on someone's car, just because they want to know where someone is."

The statute exempts parents who want to lojack their own kids, individuals or businesses who want to track their own vehicles, and of course, law enforcement. But private investigators, who make routine use of GPS trackers in their work, have been left out, and are fighting to get their own exemption written in.

It does make you wonder, though: if legislators think that we're entitled to drive our cars without fear of being electronically tracked, doesn't that amount to an acknowledgment that our "expectation of privacy" even in our public travels is "reasonable"? The legal rationale for saying that it isn't, stretching back to the Supreme Court's 1983 case U.S. v. Knotts, has always been that tracking devices only monitor the public behavior that could be observed by ordinary physical surveillance. Nobody thinks it's a secret that they're driving down a public street in plain view, right?

Sometimes, however, such easy analogies break down when dealing with new technologies—a fact courts have always been slow to recognize. A citywide network of closed-circuit cameras may only capture "public" events, but couple ubiquitous monitoring with a permanent—and in principle searchable—database of those events, and you've eroded a form of privacy people have traditionally enjoyed in practice, even when they're in public. It might be possible in principle to tail a car 24 hours a day, seven days a week without being detected, but the practical barriers to doing so provide a form of de facto privacy protection that tracking technology removes. Instead of asking whether private investigators in Georgia need their own exemption from the lojacking ban, maybe we should be asking whether law enforcement officers do.