Landgraviate of Hesse-Kassel
On 23 June 1828 Rieger, at age 76, was appointed bishop of the newly established diocese of Fulda. He was ordained on 21 September 1829 by Johann Baptist von Keller. He established some of his principles in his first pastoral letter. During his short tenure as bishop, he acted contrary to the decisions of the Landgraviate of Hesse-Kassel on a number of occasions, including: