Canon Law, the law of the Church, states that if those who come to an apparition site are from the diocese, the local Bishop investigates and decides on the authenticity. If the pilgrims come from other parts of that country, the Bishops from that country investigate and decide. If pilgrims come from different countries from around the world, Rome investigates and decides.
The Bishop of Mostar in Bosnia disapproved of the reported apparitions in Medjugorje. However, since pilgrims come to Medjugorje from around the world, his views were merely a personal opinion. The official position of the Church is made by Rome, which has done extensive investigations and could find nothing that even suggested demonic or human origin. The official position of the Church regarding the reported apparitions in Medjugorje is “not approved.”
Not approved is not the same as disapproved. Not approved is a positive statement: “We’ve checked extensively, but haven’t found anything wrong yet. We’re still looking. We’re not yet ready to say that it is truly of Divine origin.”