Sanadon entered the Benedictine order and he was principal of the college of Pau, having been a professor of history and literature.
In 1785, Sanadon published an essay on the nobility of the Basques, which he extracted from manuscripts of papers knight Jean Philippe de Bela.
[3] He was attracted to the ideas of the Revolution and he took the citizenship oath and was elected constitutional bishop of the Lower Pyrenees on 2 March 1790.
[5][6][7] On 4 September 1792, the electorate in ‘‘Basses-Pyrénées’’ chose him to sit in the National Convention (the first of 6).
He resigned on 13 August 1793 and he returned to Bayonne, where he was detained for several months in the Citadel of the Holy Spirit in 1793 and released in 1794, then went to Spain.