The new civil authorities had demanded the singing, at the end of Mass on the feast of August 15th, of the verse Domine salvum fac regem Ludovicum Philippum [ed. God save the King, Louis Philippe]. Bishop Fortuné was faced with a difficult decision in Marseilles. Eugene wrote to Henri Tempier, the other Vicar General of the diocese:
I quite expected the difficulty which would face you on the 15th in regard to singing the “Domine salvum fac.” I prefer the conclusion more than all the reasoning and (views of) authorities which preceded. Your council will certainly derive consequences therefrom which I would certainly not wish to adopt. I see in them the doctrine of the de facto government.
Letter to Henri Tempier, 19 August 1830, EO VII n 357
Leflon gives the background:
Deeply affected by the fall of the Bourbon dynasty, which, in his eyes, presaged the return of 1793 and a new persecution of the Church, Fortune was faced with an added problem of deciding what official position he should adopt toward the new regime, since Lieutenant-General Delort, Commandant of the Eighth Division at Marseilles, suggested that the Bishop order the Domine salvum fac regem to be sung on August 15, for Louis Philippe whose rule had been announced at Marseilles two days earlier. It was a grave matter of conscience for the prelate which he was unable to settle one way or the other without declaring himself for or against the Orleans regime which, through rioting, had replaced what was considered the legitimate dynasty. A diocesan council, held at the bishop’s palace, favored compliance with the General’s orders until someone suggested a way to escape the dilemma: the prayer for the king would be limited to the singing of the Exaudiat without any mention whatever of the head of the government by name. Until the Pope made an official pronouncement, the clergy were to adhere to this formula.
Father de Mazenod was not at all satisfied with this maneuver. Adroit as it may have seemed, this method of avoiding the issue still was tantamount to a first concession which was bound to lead to others far more serious, only to end in complete submission.
Leflon 2, p. 343