I want to say at that outset that I do not own an All-Terrain Vehicle (ATV), and as far as I can remember I have never even riden one. I remember that some neighbors of mine growing up had one, and it looked like fun, but my parents wouldn't let me anywhere near it. So, it is not out of any deep personal affection for the ATV that I keep urging that, before law-enforcement officials stop and question ATV driver, they need to have a reason. The Fourth Amendment says that in order to be lawful, a search or a seizure must be reasonable, and in most instances, the complete lack of a reason means the stop is not reasonable. This is not too difficult.
Currently, Maine law requires that game wardens and other law enforcement have "reasonable suspicion" before stopping and questioning an ATV driver (or any motor vehicle, for that matter). "Reasonable suspicion" means more than a mere hunch. This does not require officers to have proof of wrongdoing, or even to have "probable cause"--it is just a reasonable suspicion, supported by facts that the officer can explain later if she or he has to. "The driver was operating the ATV in an eratic manner" or "the driver was on private property and the property owners said they did not give out permission" or "the driver appeared to not have proper headgear" or "the driver appeared to be under age" are all explainations that could satisfy the requirement of "reasonable suspcion".
In an amicus curiae brief last year, the ACLU of MAINE urged the Law Court to require game wardens to have reasonable suspicion before stopping an ATV. Three of the Justices agreed with that position, though unfortunately in this instance three was not a majority. But, the legislature was willing to inact that requirement as a statute, which the governor signed into law. Let's hope that this year, they are willing to preserve it.