This excerpt, confirming what knew of Fr. Rostand's error in demanding we ignore what became public, was posted by our friend Lord Phan. May I suggest that all of you send this quote to Fr. Rostand <frarostand@sspx.org>?  You might also send it to your Catholic friends, publications, and parish email lists. We must resist the works of darkness and despotism.

CHAPTER V
ON SECRETS

i. A SECRET is some hidden matter concerning another which
cannot be made known without causing him injury or dis-
pleasure. Besides the secret of the seal of confession, which
is treated of elsewhere, divines distinguish three kinds of
secret : the natural secret, the promised secret, and the secret
which is communicated under an express or implied contract
of secrecy.

When we come to the knowledge of something concerning
another which cannot be made known without causing him
injury or displeasure we are under the obligation of a natural
secret not to make it known. This obligation arises from
charity and justice, inasmuch as these virtues forbid us to do
anything to the hurt or annoyance of our neighbour.

If we come to know something concerning our neighbour
and then give a promise not to reveal it to others, we are
bound by a promised secret. If the matter was of its nature
secret, there would be the obligation of a natural secret inde-
pendently of the promise. When the promise is given, a
special obligation arising therefrom binds the party to secrecy.
In case the matter was not of itself secret, the only obligation
would be that arising from the promise. It depends to some
extent on the intention of the promisor as to what obligation
he takes upon himself by his promise. He may intend to
bind himself to keep his word by the virtue of fidelity, because
it is the duty of an honest man to keep his promise. In this
case, as fidelity only binds under pain of venial sin, there will
only be this obligation to observe the promised secret. How-
ever, if the other party to whom secrecy was promised would
suffer serious loss from the violation of the secret, or if the
parties were bound by mutual promises, then justice would
require the secret to be kept, and the violation of the obligation
would of itself be gravely sinful. Apart even from these
circuмstances, the promisor may intend to give the other a
right to secrecy in justice, and then he will be bound to observe
it under pain of mortal sin.

A secret which is confided to another under the condition
that secrecy is to be observed constitutes the matter of an
onerous contract and binds more strictly than either a natural
or a promised secret. Such are secrets of office which officials
of all sorts become aware of in the execution of the duties
entrusted to them; professional secrets of doctors, lawyers,
priests, and others, who are consulted as experts by people
in doubt or difficulty ; as well as all others which are entrusted
to any person under the express or implied condition of
secrecy.

2. The obligation to observe a natural secret will cease after
the secret has become public property. The party whose
secret it is may sometimes be reasonably presumed not to be
unwilling that the matter should be communicated to another,
as, for example, to somebody who can and who will be of
assistance to him. If the public good requires that the secret
should be made known in order to prevent public wrong,
the obligation of secrecy will cease, for the public welfare is
of greater importance than that of an individual. If serious
harm threatens one's self or some other innocent person, or
the party whose secret is in question, and the harm can only
be averted by making known the secret, this will be allowed
in the case of natural or promised secrets. The right of
defence from impending evil prevails over that of natural and
promised secrets.

Even the obligation of the third class of secrets will cease
when they cannot be observed without serious harm to the
public weal. The natural law, however, which requires that
people should be able to consult others in their difficulties in
all security, demands that this class of secret should be observed
in the case when even serious harm threatens some innocent
person, unless he whose secret is in question is the cause of
the impending evil. Thus, if I know as a professional secret
who is the real culprit in the case of a crime wrongly imputed
to an innocent person, I may disclose the real culprit if by
some special means he caused the false accusation of the
innocent person, otherwise I must keep the secret. It is a
disputed point among theologians whether I am bound to
observe a secret at the peril of my life when it was entrusted
to me under that express condition, some maintaining that
no one can pledge his life in that way, others more probably
holding the contrary.....

A MANUAL OF MORAL THEOLOGY
REV. THOMAS SLATER, SJ.
VOL I.
FIFTH AND REVISED EDITION
LONDON
BURNS OATES & WASHBOURNE LTD.
PUBLISHERS TO THE HOLY SEE
1925
pages 394-395