First of all, as was already discussed in greater detail in “Can a Priest Ever Return to the Lay State?” once a man is ordained a priest, his priesthood never becomes invalid (c. 290). This is a legal concept firmly rooted in Catholic theology: the Church teaches that ordination—like the sacraments of baptism and confirmation—confers a permanent ontological change on the person receiving it. That’s why these sacraments cannot be received more than once (c. 845.1; cf. also Catechism of the Catholic Church 1582).
It logically follows that once a man is validly ordained a priest, he will always be a priest, and (as per canon 1338.2) no one on earth can take that away from him! Nevertheless, it is canonically possible for an ordained Catholic priest to return to the lay state: Rome can, if it so decides, release a priest from the duties and obligations which are connected with being a cleric (see “Can a Priest Ever Return to the Lay State?” for more on this). Sometimes this is done because the priest requests it; other times, as discussed in “What Does it Mean to Defrock a Priest?” it is imposed as a penalty—but regardless of who initiates it, the end-results are canonically the same.
One result, which is relevant to Patrick’s question, can be found in canon 292, which notes that a priest who has lost the clerical state is prohibited from exercising holy orders. This means, of course, that he must not administer the sacraments, is not permitted to preach, and may not bless anyone/anything. The canon observes that there is only one exception to this rule: in accord with canon 976, a laicized priest is able—and in fact is obliged—to hear the confession of a person in danger of death who requests it. This is because the spiritual well-being of a dying person “trumps” the laicized priest’s obligation to refrain from priestly ministry. (See “Can All Priests Always Hear Confessions?” for more on this scenario.) But apart from this uncommon situation, a priest who has returned to the lay state is not permitted to celebrate the sacraments. Once he has been laicized he is, in short, supposed to be living his life as any other member of the laity.
And after saying all that, it remains that there is nothing the Catholic religion can do to prevent a priest, anywhere from turning a wafer into Jesus Christ...And that creates quite a dilemma for your religion...
And look at the ramifications...If a bishop leaves for a Protestant religion, the bishop still has the authority to ordain priests in the Protestant religion...
But what is not being mentioned is that of the mind of the renegade priest...A former Catholic priest in a Protestant denomination has admitted to himself that that there is no change in the bread and wine when he prays over it...
This would have been realized that the bread and wine never did change...It doesn't look any different to a priest than it does any one else...It still looks like bread and wine...I'd bet there are untold numbers of priests out there who don't really believe that the bread and wine turns into flesh and blood but they don't dare let on to the laity...
Worrying about a former priest using his 'special' gifts is a waste of time...A born again priest is not going to waste his time with things he doesn't believe in like the Catholic Eucharist and worship of Mary and man made idols...
They do however have to come up with some answers to placate those who would ask questions about while trying to keep your religion is somewhat of a good light...