Correct me if I'm wrong here, but ultra vires, in the legal sense, is Latin for, well, going beyond one's powers. Such as (but not, as far as I know, limited to) exceeding one's Constitutional authority. Therefore, we cannot reasonably expect such a case to become a precedent for future cases of the same nature.
EDIT: BtW, what kind of person brags about driving on the wrong side of the road - TWICE - and getting away with it, FFS? Only time I ever saw that happen, I hadn't even gotten the phone to my ear to make sure there was a dial tone before I heard the crash. And, yeah, I suppose someone, somewhere might have felt sorry for that old bird, seeing as how she's spending the rest of her days in a wheelchair because of it. Me, I don't have an atom of pity for her... All mine went to the poor kid in the back seat who became both an only child and an orphan at the same time when the woman killed both his parents in the front seat and his sister, who was in the back seat with him. Stuff like that, IMHO, is like driving drunk - they shouldn't prosecute the miscreant, they should just shoot them in the head before they manage to kill someone.