Something is not right here; The Open Fields doctrine, as I recall, applied to what you could observe from outside the property or within the public air space. These guys had to trespass in order to install these cameras. If trespassing does not apply to game wardens who are not at the moment observing a violation, then I am not aware of such a ruling. There is something called "trespass of necessity", which will allow law enforcement to enter public property to apprehend a fleeing suspect, or for fire fighters to gain access to a fire, but I don't see this being applicable here. And you can't remove a tracking device from your vehicle? Even if they had a warrant, it sounds pretty iffy to me.