Birth. January 3, 1737, Minfeld, diocese of Speyer. Son of Daniel Häffelin, landschreiber, and Elizabeth Schönlaub. His name is also listed as Kasimir Johann Baptist.

Education. Studied at the University of Pont-à-Mousson; at the University of Heidelberg, where he obtained a doctorate in theology in 1765; and at the University of Ingolstadt, where he earned a doctorate in theology on November 5, 1781.

Priesthood. Ordained, September 24, 1763. In 1767, he was named chaplain of the court of Karl Theodore vom Bayern, Palatine elector; and member of the Academy of Sciences, where he presented a dissertation against the taste for Gothique and the use of German in literature. Transferred to Münich in 1778 (1), he was successively named vicar general of the Grand Priorate of the Sovereign Order of Malta in Münich in 1782; vice-provost of the collegiate church of the Blessed Virgin Mary in Münich and vice-president of the ecclesiastical council of Münich in 1783. He was ennobled, together with his brother Daniel, in 1790. Vicar general of the Anglo Bavarian parish church of St. John of Jerusalem. Domestic prelate of His Holiness, September 28, 1787.

Episcopate. Elected titular bishop of Chersoneso, September 28, 1787. Consecrated, November 11, 1787, church of Saknt Michel, of the grand priorate of the Order of Malta, Münich, by Cesare Zoglio, titular archbishop of Atena, nuncio in Bavaria, asisted by Fr. Gritz, abbot of the monastery of Benedikbeuron, and Canon Toepsi, provost of the Canons Regular of Polling. He resided in Rome from 1796 to 1798 as chaplain for the Bavarians of the Order of Malta. At his return to Bavaria, following the occupation of Rome by the army of the French Directory, he was named librarian of the court of Bavaria (Oberhofbibliotekar) for Duke Maximilia Joseph in 1799. After the first restoration of the papal government in Rome, he returned to the city as plenipotentiary minister of the king of Bavaria before the Holy See from 1803; he tried to conclude a a concordat, based on the model of the Napoleonic one, but the negotiations were interrupted by the French occupation of Rome. He retired to Naples, where he was accredited as ambassador in 1810. After the restoration of the papal government in Rome, he returned as plenipotentiary minister in 1815 and kept the post until his death. He successfully concluded the concordat between Bavaria and the Holy See, which was negotiated with Cardinal Ercole Consalvi, secretary of State, and signed on June 5, 1817.