[1] Sibour was part of the ministerial commission which prepared the draft project for the Falloux Laws on education, which highly increased the clergy's influence in schools.

[1] Although in his answer to Pope Pius IX he declared the definition of the Immaculate Conception inopportune, he was present at the promulgation of the decree and shortly afterwards solemnly published it in his own diocese.

On 13 May 1856, he granted Peter Julian Eymard permission to found in the Archdiocese of Paris a new Religious Institute, which became known as the Congregation of the Blessed Sacrament.

Sibour was assassinated at the church of St. Etienne du Mont by an interdicted priest named Jean-Louis Verger, who openly admitted to the crime.

When he was executed at La Roquette Prisons on 30 January 1857, he was in a state of panic and fear due to the failure of the pardon to come.