What countries did the Habsburgs rule ?
He devoted his 1764 work " De Originibus et Usu perpetuo ... " ( " On the Origins and Perpetual Use of the Legislative Powers of the Apostolic Kings of Hungary in Matters Ecclesiastical " ) to argue for the supremacy of the Habsburgs ' rule over the Roman Catholic hierarchy , over the traditional legislative powers of the Kingdom 's Diet and , indirectly , over the privileges of its nobility .