Why did the Magna Carta fail to prevent civil war in England?

The Magna Carta failed to prevent civil war in 1215 primarily because it was rendered unworkable by both the intransigence of certain barons and King John’s immediate appeal to Pope Innocent III to annul the agreement.1

The failure was driven by several key factors:

• Papal Intervention: Because John had previously subjected England to the papacy as a fief, he held a strong alliance with the Pope. Innocent III declared the charter null and void, arguing that it violated his rights as the king's feudal lord.12
• Lack of Trust: While the charter was intended as a compromise to limit royal power and ensure the rule of law, the most extreme members of the baronage remained committed to conflict rather than negotiation.3
• Escalation: The implementation of the charter, particularly Clause 61—which authorized the barons to declare war on the king if he breached the agreement—proved to be a source of immediate friction rather than a mechanism for peace.3

Ultimately, the document served only as a stage in ineffective negotiations, and the ensuing civil war continued until after John’s death in 1216.14