However, over the past three decades, unauthorized translations have appeared around the world, according to Cardinal William Levada, prefect of the Congregation for the Doctrine of the Faith. The doctrinal office "believes it is now opportune to publish these 'Norms,' providing translations in the principle languages" so as to "aid the pastors of the Catholic Church in their difficult task of discerning presumed apparitions, revelations, messages or, more generally, extraordinary phenomena of presumed supernatural origin," the cardinal wrote in a note dated December 2011.

His note and the newly translated norms were published recently on the congregation's web site www.doctrinafidei.va.

Levada wrote that he hoped the norms "might be useful to theologians and experts in this field of the lived experience of the Church, whose delicacy requires an ever-more thorough consideration."

More than 1,500 visions of Mary have been reported around the world, but in the past century only nine cases have received Church approval as worthy of belief.

Determining the veracity of an apparition falls to the local bishop, and the Vatican's doctrinal congregation established the norms to guide the process.

Granting approval is never brief, with some cases taking hundreds of years. Visionaries and witnesses must be questioned and the fruits of the apparitions, such as conversions, miracles and healings, must be examined.

According to the norms, the local bishop should set up a commission of experts, including theologians, canonists, psychologists and doctors, to help him determine the facts, the mental, moral and spiritual wholesomeness and seriousness of the visionary, and whether the message and testimony are free from theological and doctrinal error.

A bishop can come to one of three conclusions: He can determine the apparition to be true and worthy of belief; he can say it is not true, which leaves open the possibility for an appeal; or he can say that at the moment he doesn't know and needs more help.

In the last scenario, the investigation is brought to the country's bishops' conference. If that body cannot come to a conclusion, the matter is turned over to the Pope, who delegates the doctrinal congregation to step in and give advice or appoint others to investigate.

The alleged apparitions at Medjugorje in Bosnia-Herzegovina are an example of a situation in which the country's bishops requested the Congregation for the Doctrine of the Faith to intervene. In that case, the congregation established an international commission in 2010 to investigate the claims of six young people who said Mary had appeared to them daily beginning in 1981. The apparitions purportedly continue and thousands travel to the small town each month to meet the alleged seers and to pray.

Pope Benedict XVI has reaffirmed that the Church never requires the faithful to believe in apparitions, not even those recognized by the Church.

In his note, Levada quoted the Pope saying "The criterion for judging the truth of a private revelation is its orientation to Christ Himself," in that it doesn't lead people away from Jesus, but urges them toward closer communion with Christ and the Gospel.

The cardinal also quoted from the writings of St. John of the Cross, who emphasized that God said everything He had to say in Jesus Christ — in His one and only son and Word.

"Any person questioning God or desiring some vision or revelation would be guilty not only of foolish behaviour but also of offending Him, by not fixing his eyes entirely on Christ and by living with the desire for some other novelty," the saint wrote.

Church approval of a private revelation, in essence, is just the Church's way of saying the message is not contrary to the faith or morality, it is licit to make the message public "and the faithful are authorized to give to it their prudent adhesion," the Pope said in his 2010 Post-Synodal Apostolic Exhortation, "Verbum Domini" ("The Word of the Lord").

The text of the Vatican norms in English is available online here.