@collectedoverspread I'm not sure if it has an official name, other than like "missing the point".
It needs a bit more to be a good argument: it implies that a law won't do X amount of good; ok fine – the obvious thing you need to examine is how much good, <X, *will* it do, then? And weight that against the costs. So it's like just the first part of a coherent argument, at best.