After the sudden death of Ladislaus, William returned to Hungary and swore loyalty to Andrew, who ascended the Hungarian throne.
[4] During William's episcopate, King Andrew II of Hungary granted the region Burzenland (Barcaság, present-day Romania), the sparsely populated southeastern part of Transylvania, to the Teutonic Order in 1211.
According to historian László Pósán, William, while provided many discounts to the Teutonic Order, clearly outlined his powers and authority as diocesan bishop over Burzenland.
[8] The cordial relationship between William and the Teutonic Order had deteriorated from late 1216, when Pope Honorius prohibited the knights from accepting conditional grants from secular sources.
The Holy See decided to exempt the Teutonic Order from episcopal authority everywhere in October 1218, which also affected negatively William's ecclesiastical jurisdiction over Burzenland, despite the aforementioned confirmation of his 1213 privilege letter.
[9] Similarly to his predecessor Adrian, William had a violent conflict with the Kolozsmonostor Abbey, disputing the Benedictines' privileges and exemptions.