I see what your saying but the only way that could be enforced is if the hogs were in captivity which opens another can of worms in which if they were in captivity your holding pens would have to be inspected or if they got on the road and a car hit one they could sue you.
If the pig gets on the road and gets ran over it would no longer be on a land owners properties making it no ones hog until it is back on private property