On 12 July 1790, the French National Assembly passed the Civil Constitution of the Clergy which placed the Catholic Church in France under the authority of the French government.
The National Assembly, dominated by representatives who had been deeply inspired by the Enlightenment’s anti-Catholic views. Since France was struggling with a deep debt, they believed the best way both to weaken the power of the Catholic Church as well as to help solve the problem of the French debt was to restrict the power of the French Catholic church both politically and economically.
Therefore the Civil Constitution nationalized all Church property, bishops and priests were no longer appointed but instead were to be elected [moreover the electors did not have to be Catholic], no longer would the Pope have any voice in the election and appointment of bishops in France and all clergy were to sign an oath of loyalty to the Civil Constitution and the French Government.
Needless to say, Pope Pius VI vehemently opposed the Civil Constitution and warned the clergy that anyone who swore an oath to it would be excommunicated. The vast majority of bishops of France refused to agree to the Civil Constitution but the majority of priests did accept it. Thus a schism was created in the French Church between the those who swore the oath to the Civil Constitution and those who refused to do so. This schism would not be resolved until 1801 when Pius VII and Napoleon I agreed to a new relationship between the French Government and the Papacy.