Is it illegal for somebody to put a GPS locator on your car without permission?

I feel you have a right to privacy if you are not under the age of 18 and the people that is trying to track you is not a family member.
First question I need to known is WHO does the CAR that is being track belong to? If it is his car than he is not breaking any law since he has a right to put a tracking system in his vehicle.
Is the car a used car that was purchased? If yes and if he holds the title to your car, than he also have the right to track it.
Tracking via GPS is done everyday, your GPS enable cell phone can track you, the OnStar in your vehicle can track you also. So we are being tracked all the time without us knowing it.
Some rental car companies and used car sales company will have a tracking system install in your car so they can repossess it should you not make your payment.
What is the reson he is tracking you that you should worry about, if he is stalking you and using this device to invade your privacy, than he is breaking the law and your right to privacy.
I can tell you that jealous husbands or boyfriends and wife’s or girlfriends routinely track their partners, but you have to know that some wish to do it for your safety and other wish to do it because they are afraid that you maybe dishonest to them.

File a report with the PD and go to a 12 volt retailer that have tracking system installation knowledge to see if you can locate the tracking device.

It is morally hidden above the radio, above the glove box panel, above the P/S airbag, in the center console, near your rear speaker facing out towards your rear window etc. This is if the unit is a transceiver and can track you via Internet.
Here are some pictures of the Santa Clara County Auto Theft bait car we installed a tracking system for Photo Gallery / Emergency vehicles / Santa Clara County Bait car.

http://www.autonav2000.com/PhotoGallery/Thumbnails/Santa_Clara_County_Vehicle_Theft_Unit_Bait_Car

http://www.autonav2000.com/PhotoGallery/Emergency.htm

The lower end tracking recording device is the ones that you have to remove and download where you have been on a computer and watch where you have been to during the day.

Best way to verify is to watch and see if he is tempering with your vehicle at any time, keep your vehicle locked and whenever he is around, look to see if they want to get into your car for no good reason. Go with them to the car if you are going to let them get in your car.

The vehicle tracking system can be hardwire to the car power source which they will not need to charge the tracking system and remove it frequently. But they must have had the possesion of your vehicle for a few hours if they are able to install a hard wire tracking system in your vehicle.

Think when was the last time this person had your vehicle and for how long?

Have someone look under your vehicle and see if you can locate any type of small black box, the tracking unit can go for a few weeks to a month without needing to be recharge.

If you wish to view how small a tracking system can be and what the case may look like, you can view the image at Auto Nav 2000 Plus, Inc.

http://www.autonav2000.com/mall/anProdList2.asp?GroupID=194

If you file a report with the PD, it may scare him off enough to have the device removed.

Good Luck