Which system required free men to pledge loyalty to the king's laws and maintain local peace?

The Frankpledge System is the correct answer because it was a form of social organization prevalent in medieval England that required groups of free men to band together in a pledge of loyalty to the king’s laws and to help maintain local order. Under this system, each member of the community was responsible for the behavior of their peers, effectively creating a system of mutual accountability. This structure aimed to ensure that individuals took an active role in law enforcement and community safety, aiding in the maintenance of peace and adherence to the king’s directives.

The other systems mentioned, while related to law enforcement and community safety, do not specifically encompass the same pledge of loyalty and accountability among free men to uphold the king’s law and maintain local peace.