The very simple and sure answer is "No". A Catholic openly promoting the events in Medjugorje is committing the very serious sin of disobedience at an absolute minimum.
Though it is true that those who have truly studied Medjugorje- as I have- are acutely aware of the sordid history. We are aware of the rebellion and the disobedience, the sharp rise in occultist activity, sins of the flesh, graft, corruption, heresy and outright disobedience that are the hallmarks of these events.
We are also aware of the 5 priests from the very inner circle of the visionaries that have been laicized, excommunicated and even exiled for impurity, heresy and conjuring up spirits.
These penalties have been enforced by the Vatican. The case of Father Jozo Zovko is just one tragic example.
We are also aware that 40+ years of these reported events have failed to produce one miracle approved by the church, one miraculous cure approved by the church or even one prediction that has proven to come true. It is well publicized that the visionaries have lied and changed their stories and have been uncooperative with the investigators in virtually every regard. This includes with the revealing of the so-called secrets and participating in medical tests during the so-called ecstasies.
Experimentation and observation have proven Medjugorje to be fraudulent in every way imaginable. The famous "fake ecstasy" video of alleged seer Vicka provides particular damning proof. Her scandalous explanation is even worse.
Of course, Vicka and the other 5 seers probably care not whether you believe them. They are all millionaires in mansions thanks to the money they have made from these events. They all live quite lavishly. One of them owns a $1.5 Million home on the outskirts of Boston that was paid off in under a year using Medjugorje funds.
Many people are shocked and stunned to hear these facts. They are not to be blamed. Not everyone's life permits them the luxury of investigating each of these alleged events as thoroughly as I have. That no faithful and reasonable Catholic could know these things and still support this abomination goes without saying. There are a few who do. Sadly, they will answer for this grave evil if they do not repent.
What about the rest of you? What about those who do not know all the sordid details of Medjugorje but have only heard of it as a place of prayer and conversion? You may have some anecdotal experience that you heard. Maybe Aunt Betty had a friend who went to Medjugorje and experienced a sense of peace. Maybe someone from your co-worker's church went there and saw a Rosary turn gold. Maybe someone was personally converted back to the Catholic faith because the Holy Spirit reached them in that place or through someone or something connected to it.
Maybe all of these things have convinced you that, in some way, some day, despite everything that has occurred up to now, the Vatican will approve these events.
How would I respond to your belief? I have to be honest. After everything that has transpired and been put out, belief that Medjugorje will be approved can only be the result of misinformation, delusion or some type of an agenda by which you would personally benefit such as book sales.
Nevertheless, as delusional as it might be, the belief that Medjugorje will one day be vindicated- as-true is not, in itself, sinful. It is said that reading a book about Medjugorje contributed to the conversion of Father Donald Calloway (above). Since I have no firm evidence for or against this claim, I am just going to assume the rumor to be true for the purpose of moving the conversation forward.
It is possible that the rumors are true and Father Calloway once believed that Our Blessed Mother has appeared in Medjugorje in the former Yugoslavia.
I am even willing to stretch the point- for the sake of argument- and say that perhaps he still believes it (though I personally find this very doubtful).
Would this make him a dissident priest like the 5 suspended in connection to Medjugorje?
No. Here is why.
Unlike the 5 Medjugorje priests that have been formally disciplined by the Vatican, Father Calloway has not committed a sin even if (and it's a BIG if) he still does believe Our Blessed Lady has appeared in Medjugorje.
I'm not even referring here to the sexual indiscretions or conjuring up spirits or the kidnapping of a member of the clergy. Those are discussions for another day. What Fathers Jozo Zovko, Father Ken Roberts, Father Tomislav Vlasic and Fathers Vega and Prussini (these last two led the kidnapping mob) are first and foremost guilty of is the sin of disobedience. This is the sin that fractures the Body of Christ. In defiance of the Bishops, these priests have been promoting the condemned events in Bosnia. This is what you will not see Father Calloway do.
As I have said before, I cannot confirm if Father Calloway still privately believes in Medjugorje. My guess would be that he does not. However, that guess would be only that- the guess of a fallible man. In terms of making an argument, it would be better for me if it were true that he believes because it just hammers the point home that much more succinctly.
On Father's website, you can see all kinds of things. He gives his Biography- which has no mention of Medjugorje. He lists events and speaking engagements. Not a syllable of Medjugorje. Books and Gifts? Lots of stuff on Saint Joseph, Guadalupe, Divine Mercy...
Vocations? Not a mention of Medjugorje.
What about Pilgrimages? Surely he would mention it here. Medjugorje adherents like to boast that pilgrimages are allowed there. Does Father Calloway sponsor pilgrimages to Medjugorje? He does not.
The same is true for all of the other clergy that supposedly were privately devoted to Medjugorje. Medjugorje proponents have long held that Pope John Paul II was a secret supporter of Medjugorje. This is a dubious claim at best. In 25 years in the Papacy, JP2 never once visited Medjugorje and never once publicly endorsed it. Claims that the Holy Pope was a secret Medjugorje supporter are nothing more than unsubstantiated nonsense.
Renowned Catholic Apologist Patrick Madrid says the following on his own website:
All the stories I have heard from Medjugorje supporters about how Pope John Paul II favored or even personally believed in its authenticity have all been apocryphal. I am not aware of the Holy Father ever publicly commenting, one way or the other, whether verbally or in writing, on Medjugorje.
Sure, there are numerous instances of private comments alleged to have been made by JPII about Medjugorje, but none that I am aware of which have been verified with documentation, such as video or audio recordings. Peruse these comments, and you’ll see they are all third-hand. He said he said he said, etc.
The fact is (and it is really indisputable) that every binding public pronouncement of the church on Medjugorje has been negative.
These are not the pronouncements that you may follow or should follow, these are the pronouncements that you must follow.
These are the words of the 3 sitting Bishops of Mostar since 1981. Bishops Zanic, Peric and Palic have been unwavering.
There has been nothing supernatural found to have occurred in Medjugorje.
The Virgin Mother has never appeared in Medjugorje, not even once.
These findings were ratified 4 times including the most recent officially in 1991 by the Yugoslav Bishop's council by a vote of 19-0 which was followed up in confirmation by then Bishop Peric and recently by current Bishop Palic.
5 1/2 years ago, the Ruini report recommended the ban be removed on a total of 7 apparitions (out of some 50,000+ that are alleged to have occurred. The report was not well received and the Vatican has not adopted the recommendations. To this day, Medjugorje remains an officially condemned event and no Catholic may promote it under penalty of grave sin.
This is currently the statement that appears on Catholic Answers
This is not what was only the Catholic Answers site 20 years ago or even 5. This is what appears there today.
So, what is the answer to the original question?
A Catholic who is knowingly promoting Medjugorje, with full knowledge and deliberate consent is committing deliberate mortal sin.
Sorry. It really is that simple.