In most places the state, city, or county owns everything from the center of the road for so many feet in each direction. The exact distance varies, but it is usually a pretty fair distance.
Whether it is "most places" or not, by the numbers there ARE places where things are a little different and you need to know if one of those places is where you live, and, if in this case, the location the incident took place is, or not.
What I'm talking about is technical "ownership" of property, and whether or not it is a legal fiction, or an actuality where it matters.
While many people assume the city/county/state "owns" the road and X number of feet to either side, they may, or may not actually "own it". Certainly they have the practical control of it, and the right of easement (or what ever the proper term is), but they may have only that and the actual ownership is private.
To be certain, find out what is in the county tax records for the property in question, and then, find out if what is in the records is what is correct, or not. It may not be.
A few years ago, due to a dispute with a family member/neighbor I had to get my property surveyed. Paid the professionals to do it, got the result and then found I had to pay more to get the correct survey recorded in the tax books, but it was done. Among other things the survey determined was that my property runs to the middle of the county road. I OWN that land, legally, and it IS counted as part of my property for tax purposes.
However (and really, rightly so) the county "owns" the road, and a certain distance from the edge of the road to do with as they please. They don't own the land the road is on, technically but for practical purpposes, they do.
SO, it is possible to be on what is regarded as public property, but is actually private property at the same time. Which one of those will have precedence in a legal proceeding such as the one under discussion here, I do not know and I expect there will have to be a court ruling on the matter, if there is some kind of case where I am violating the law if it is public but not if its private and I own it.
I do not have any idea if it applies to this case of the GFSZ law, or not. I am only pointing out that there might be a place and circumstance where legal ownership of the property
might be a deciding factor.