The Vatican has issued a statement saying that in order to serve in the Roman Catholic Church, Holocaust denying British Bishop Richard Williamson must "unequivocally" distance himself from his statements, including those that no Jews died in concentration camp gas chambers. Williamson has publicly said:

I believe that the historical evidence is strongly against, is hugely against six million Jews having been deliberately gassed in gas chambers as a deliberate policy of Adolf Hitler..I believe there were no gas chambers [during World War II]…300,000 Jews perished in Nazi concentration camps but not one of them by gassing in a gas chamber.

Earlier this month Pope Benedict XIV had lifted Bishop Williamson’s excommunication; he and four others had been consecrated without papal consent 20 years ago by the late French ultraconservative Archbishop Marcel Lefebvre and are members of the Society of Pius X.

The statement issued by the Vatican says:

Bishop Williamson, in order to be admitted to the Episcopal functions of the Church, must in an absolutely unequivocal and public way distance himself from his positions regarding the Shoah [Holocaust].

Additionally the statement said that Bishop Williamson’s positions on the Holocaust were

absolutely unacceptable and firmly rejected by the Holy Father.

The Vatican also said that the Society of Pius X must recognise the Vatican II Council of 1962-65–which modernized the Catholic litury and doctrine–and the popes who followed it. One change instituted by  Vatican II  was to the Good Friday liturgy, removing the word "faithless" as an adjective for Jews with additional changes made in 1970 that emphasized the  Vatican’s growing positive attitude towards the Jews and a lessening of the Church’s medieval anti-Semitism.

The BBC explained the Vatican’s shift on Williamson:

Cardinal Walter Kasper, who is in charge of relations between the Roman Catholic Church and Jewish leaders, admitted different parts of the Vatican administration had not talked enough to each other, and failed to check where problems could arise. 

In otherwords, someone dropped the Papal bulla.