Actually, LT COULDN'T do anything to Howard the Duck unless he was authorized to do so by TOAA. He'd just have to stand there and take whatever Howard dished out (which would be a lot of nothing), or just...leave. LT doesn't fight - he enforces. And he only enforces when a judgment has been made.
So I guess that means that, TECHNICALLY speaking, Howard the Duck would win, since LT would have to retreat (and attend to other business)