This chapter concludes the detailed examination of co-rule with two responsibilities most intimately connected with lordship in medieval thought and modern scholarship: war and justice. During the succession dispute, the Montfortists raised the standard complaint that a woman could not undertake these duties, but the Penthièvre case argued that inheritance and shared power circumvented this objection. Jeanne’s actual engagement with responsibilities of jurisdiction and warfare demonstrates that although her role expanded in Charles’ absence, she continually acted in her own right rather than as a proxy or intercessor, two dynamics strongly linked to women’s exercise of power (and particularly to queenship). This independence allowed Jeanne to use power-sharing as an active strategy to stabilize her and Charles’ position during periods of protracted negotiations, as two case studies show. At the same time, theoretical and practical distinctions made between performing these seigneurial responsibilities in service to one’s lord, and one’s own exercise of lordship, embedded the gender dynamics of spousal co-rule within the negotiation of power across the French sociopolitical structure.