American scholars now argue that Magna Carta embodies a ‘proportionality principle’ mandating that the punishment fit the crime. This principle, according to a familiar narrative, found expression centuries later in the English Bill of Rights, which was reproduced another century later in the American Bill of Rights. The Eighth Amendment's prohibition on cruel and unusual punishments is thus said to originate in the dramatic encounter between the barons and King John on the fields of Runnymede. This story has proven to be of more than simply academic interest. Justices on the U.S. Supreme Court have claimed the authority of Magna Carta when infusing the prohibition against cruel and unusual punishments with a proportionality principle not immediately evident from the text of the Eighth Amendment. Thus emboldened, the Supreme Court has overturned supposedly disproportionate criminal sentences.

This essay questions much of this narrative. My claim is that the articles in Magna Carta that are now cited to stand for the principle that the punishment must fit the crime do no such thing because, at bottom, those articles do not concern criminal activity. Natalie Riendeau's contribution to this volume explores Magna Carta's role in the ‘legend and myth’ of English life (Chapter 11). This chapter supplements hers by identifying and exploring how a myth surrounding Magna Carta has shaped the discourse on the meaning of the U.S. Constitution's cruel and unusual punishments clause. Scholars and jurists have anachronistically deployed Magna Carta to resolve a contested issue of constitutional law.

My plan is as follows: the first section traces the uses made of Magna Carta by American jurists in advancing the argument that the ancient document embodies a proportionality principle. The argument has lately focused on Articles 20 to 22, which restrict ‘amercements’ to those ‘in accordance with the gravity of the offense’.