In this paper we use a series of examples to show how oppositions and dichotomies are fundamental in legal argumentation, and vitally important to be aware of, because of their twofold nature. On the one hand, they are argument structures underlying various kinds of rational argumentation commonly used in law as a means of getting to the truth in a conflict of opinion under critical discussion by two opposing sides before a tryer of fact. On the other hand, they are argument structures underling moves made in strategic advocacy by both sides that function as platforms for different kinds of questionable argumentation tactics and moves that are in some instances tricky and deceptive.