In that year, he co-signed a letter with his cousin, Philip of Montfort, and Geoffrey of Estraing to the Emperor Frederick II, nominal regent of Jerusalem.
The letter, which had the encouragement of Richard of Cornwall behind it, proposed that Frederick pardon all baronial rebels and create Simon de Montfort, Earl of Leicester, bailiff.
The barons would in turn swear oaths to Simon and recognize his authority until the young king, Conrad II, came of age (1243).
In February 1251, shortly after becoming the lieutenant (bailli) of Jerusalem on behalf of the regent Henry of Cyprus, John called a council of liegemen in the palace of his relatives, the lords of Beirut, in Acre.
In 1257, he confirmed a treaty with the city of Ancona, granting it commercial rights in Acre in return for aid of fifty men-at-arms for two years.