It is legal for the police to attach a GPS tracking device to your car parked in the driveway. That's how you protect yourself
Matt's post about the decision explains the decision in depth. As a quick recap, the Supreme Court has previously said that the police can look at anything the public may encounter, which means that your lane is free to the public and therefore the police can walk through it. The 9th Circuit now says police can put a GPS locator on your car because the area is public and you have no reasonable expectation of privacy. Then say the police can use the GPS track you are using.
How can you stop this without combing the underside of your car - or even the inside - and finding the GPS tracker?
Your first bet may be whether someone is watching you. You can view your phone and error detector here. But none of these are 100%, so if you're really paranoid and want to hide your location, you'll still want to go ahead and stop the tracker.
The first is a GPS signal jammers, which is technically illegal to buy and use in the United States, so keep that in mind. These types of GPS jammers plug into your car's cigarette lighter and "disable GPS signals" from 10 meters away.
Another less expensive GPS model only stops GPS L1 and L2, depending on the situation. However, if you want to stop every GPS transmission, you must use the TN-H062, which costs $300.
If you're worried about someone monitoring your phone, there's a signal shield bag for about $10 that you can stuff your device into when not in use.