Federal and State Laws
Private investigators routinely use GPS devices to track cars they are hired to follow. Private entities have more leeway legally than many federal and state law-enforcement agencies. In most states and by federal law, placing a GPS tracking device on a car is not illegal unless a crime is committed while doing so (breaking into the car, tampering with brakes, etc.).
Different States, Different Laws
Each state has a different set of laws regarding GPS tracking. Before you undertake using your GPS as a tracking device, consult with your local law-enforcement agency to see what the laws are in your state.
The Fourth Amendment
According to "Police Chief" magazine, in 1983 the U.S. Supreme Court ruled that the use of "bird dog" tracking devices placed in public places was not a violation of law or breach of the constitution. The Supreme Court said, "Nothing in the Fourth Amendment prohibits the police from augmenting the sensory faculties bestowed upon them at birth with such enhancement as science and technology afforded them in this case." This was in regards to law enforcement using these devices, not private entities.
Denial of Law
According to cyber crime and GOS device expert Susan Brenner of the blog CYB3RCRIM3, at least one state has ruled against law enforcement and private entities being allowed to plant and use GPS devices to track individuals against their knowing.
Backcountry Tracking Use
If you are using the GPS to track and follow backcountry adventurers in real time via websites and other electronic means, there is typically no problem. Many of the adventurers and explorers agreed to being tracked or wish to have the information available to the public. If setting up such an adventure, you are in no danger of violating laws.
Article Written By Eric Cedric
A former Alaskan of 20 years, Eric Cedric now resides in California. He's published in "Outside" and "Backpacker" and has written a book on life in small-town Alaska, "North by Southeast." Cedric was a professional mountain guide and backcountry expedition leader for 18 years. He worked in Russia, Iceland, Greece, Turkey and Belize. Cedric attended Syracuse University and is a private pilot.