"Well, if you want to get REALLY technical about it..." There's something that niggles at him about 'injustice'. Or, rather, the 'justice' part of it. But that's who he is, isn't he?

Luckily, since this is going by story book tropes, whoever tied Vance up wasn't that great at it. Or had decided that, because of the large and floofy skirts, tying up his legs wasn't a priority. And, honestly, the skirts meant that standing UP from this chair without help would be difficult.

It does mean, however, that since Videl's standing close to him? He can reach out with one leg. And, as she's turned away from him? He instead kicks out at the back of her knee.