Argumentum e contrario

An argumentum e contrario (Latin: "appeal from the contrary" or "argument based on the contrary") denotes any proposition that is argued to be correct because it is not proven by a certain case. It is the opposite of the analogy. Arguments e contrario are often used in the legal system, as a way to solve problems not currently covered by a certain system of laws. Although it might be used as a logical fallacy, arguments e contrario are not by definition fallacies