Thanks to a ruling by a federal appeals court, it's now legal in nine US States, including Oregon and California, for government agents to sneak into your driveway and plant a GPS tracking device on your car.
The U.S. Ninth Circuit Court of Appeals decided that this is not in conflict with the Fourth Amendment because "an individual does necessarily have a reasonable expectation of privacy in their driveway." That's right, your driveway apparently no longer counts as private property! Riiiight....
So every state has different property-line laws, but generally they seem to agree that property extends out to the sidewalk or street, and also to the line of the neighboring property (which would usually include the driveway). As this article in Time Magazine says, "The courts have long held that people have a reasonable expectation of privacy in their homes and in the 'curtilage,' a fancy legal term for the area around the home."
As the Time article also points out the case got its start right here in Oregon. A man suspected of growing marijuana sued after DEA agents snuck onto his property in 2007 and planted a GPS unit on the man's car.
Chief Judge Alex Kozinski, who dissented from his court's decision, has pointed out that this driveways-as-private-property issue is a class divider, because rich people have gates that make the property around their house private. Therefore, it's the poor who would suffer the trespassing of Big Brother. I mean, really, why would you monitor rich people? They never do anything wrong...
The US Ninth District Court of Appeals ruled that no search warrant or tracking warrant is needed by the government for installing tracking units on people's cars in driveways. The court said driveways already are open to strangers like delivery folk and kids. (Never mind whether you're yelling at them to get off your lawn or not.)
Hopefully other courts have a different opinion here, and this will end up in the Supreme Court where we can overturn it.