Cantarella made the following quote & cited Pope Gregory XIII's Bull regarding the problem of false conversions of Jєωs as a means to infiltrate the Church...
This is an inaccurate summary of the quotation from the
Tradition in Action article
http://www.traditioninaction.org/HotTopics/a028htJPII_VisitToѕуηαgσgυє1986.htm cited:
In the Brief of May 27, 1581, Gregory XIII (1572-1585) warned the faithful and religious authorities against the false conversions of Jєωs as a means to infiltrate the Catholic Church. (37)
In the Bull Antiqua ʝʊdɛօrum improbitas of June 1, 1581, the Pontiff established these conditions for when Jєωs must be submitted to the vigilance of the Inquisition:
a. when they attack Catholic dogmas;
b. when they invoke devils or offer sacrifices to them;
c. when they teach Catholics to do the same;
d. when they speak blasphemies against Our Lord and Our Lady;
e. when they try to induce Catholics to abandon their Faith;
etc.
The papal Bull Antiqua ʝʊdɛօrum improbitas did not say anything about a problem with false conversions of Jєωs to inflitrate the Church, nor did the TIA article claim it did. The article claims that a different docuмent, the Brief of May 27, 1981 "
warned the faithful and religious authorities against the false conversions of Jєωs as a means to infiltrate the Catholic Church."The article gives a footnote (37) to the book which supposedly supports this claim:
35. Apud L. Pastor, Historia de los Papas, vol. 17, p. 306.36. Ibid., vol. 17, pp. 306-7.37. Ibid., vol. 19, p. 281.Looking at the English translation of
Historia de los Papos, volume 19 (which clearly has different pagination)
https://archive.org/stream/thehistoryofthep19pastuoft/thehistoryofthep19pastuoft_djvu.txt there is a section on problems with conversos starting on page 308:
In the time of Gregory XIII. the Inquisition was often en
gaged with relapses into Judaism ; J these renegades, who
had accepted Christianity in Spain and Portugal, and had then
secretly returned to their former religion, frequently took
refuge from the power of the Inquisition in Spain and Portu
gal, and overran the whole of the north and centre of Italy.
Gregory XIII. addressed letters on the subject to the nuncio
at Venice, 2 and to many of the Italian princes. He warned,
for example, the republic of Genoa against receiving refugees
of this kind, without finding out definitely who they were,
whether they could produce certificates of good conduct, and
where they intended to stay ; once they had been admitted
they were not to be sent away, so that they might not take
refuge among the unbelievers....
There is a quote from the Brief of May 27, 1581 in this section which says:
Accepimus multos a ludaica perfidia ad Christi fidem recenter
converses rursumque Christo repudiate ut canes ad vomitum
suum ad ludaismum reverses quotidie ex multis regionibus
praesertim vero ex Hispania et Lusitania in Italiam confluere,
etc.
Neither this quote from the Brief, nor anything else I can find in the text supports a claim that Gregory VIII warned people that false conversions were a means to infiltrate the Catholic Church.
(English translation of Brief:
We have received many recently from Jєωιѕн perfidy to the faith of Christ, who turning around again like a dog to his vomit, are returning to Judaism, daily coming together from the many regions, especially from Spain and Portugal, to Italy.)Perhaps others could take a look through the linked material to see if I am missing something, but I do not see anything about converts infiltrating the Church.