Why is it that legislation defining the crimes of treason and sedition soon follows in the wake of the establishment of every nation-state? The answer is reasonably simple: At the heart of the question of these crimes lies the legitimacy of the State and the claims it can make upon the loyalty of its citizens. Treason has always been considered one of the most heinous crimes. Punishment has usually been capital and has at times been marked by quartering and burning at the stake.

The crime of treason is generally treated as a betrayal of allegiance - the duty and obligation of the citizen toward his State. In the laws of the Roman empire and in early British law, treason encompassed imagining or planning the death of the king, his family, or his officials; levying war against the sovereign; adhering to the king's enemies in the realm; or giving them aid and comfort in the realm or elsewhere. In the United States, which is one of the few countries to have defined treason in its Constitution, treason is confined to two specific types of action: challenging the power of the nation by armed insurrection and aiding its enemies during wartime.

Sedition is a loose concept that includes "everything whether by word, deed, or writing," which might disturb "the tranquility of the State," and lead to its subversion. In England and the United States, during the 18th Century, sedition meant any hostile criticism of the government, which the authorities might choose to prosecute. If treason could not be alleged, then people might be imprisoned for sedition, i.e., "disloyal" speeches and writings. This occurred in the United States in 1798, at the time of the Civil War, and again during World War I.