During the barons' wars la Zouche adhered to the king. He was on 9 July 1261 appointed High Sheriff of Northamptonshire, receiving in October a letter from the king urging him to keep his office despite any baronial interlopers. He remained sheriff until 1264, and sometimes ignored the provisions of Magna Carta by acting as justice itinerant in his own shire and also in Buckinghamshire and Hampshire. In 1261 he was also made justice of the forests south of Trent, and in 1263 king's seneschal. In April 1262 he held forest pleas at Worcester.