LoneRanger:
you don’t ever cease to be catholic, unless you make a formal declaration (signed) to that effect…
It is a Catholic “urban legend” that a Catholic must “make a formal declaration (signed)” to lose his or her membership in the Church.
In fact, all a Catholic needs to do to lose their membership in the Church is to obstinately refuse to accept even one infallible teaching of the Church. Such a Catholic is a heretic, and heresy carries the penalty of loss of membership in the Catholic Church through automatic excommunication.**Catechism of the Catholic Church
2089**… "Heresy is the obstinate post-baptismal denial of some truth which must be believed with divine and catholic faith, or it is likewise an obstinate doubt concerning the same …
Can. 1364 §1 An apostate from the faith,
a heretic or a schismatic incurs a
latae sententiae excommunication …
Excommunication can take two different forms. A
ferendae sententiae excommunication comes after a formal canonical trial, and is often a matter of public record. A
latae sententiae excommunication is incurred automatically, under the terms of the Code of Canon Law, as the punishment for certain offenses. In the case of a
latae sententiae excommunication, there is no requirement for formal trial or announcement; in fact, the individual brings the punishment upon himself.
Excommunication
latae sententiae is the canonical punishment for offenses such as heresy, violation of the seal of confession, or procuring an abortion. **Catholics guilty of these offenses are excommunicated automatically, even in cases when Church authorities are unaware of their offense. **
cwnews.com/news/biosgloss/definition.cfm?glossID=91]Catholic World News
**Do sinners continue to belong to the Church? **
Unless one cuts himself of by
heresy, apostasy, or excommunication, a Catholic sinner continues to be a member of the Church. Those in mortal sin remain united by faith and hope, but not charity.
Most Reverend Lois Laravoire Morrow, S.T.D., Bishop of Kishnagar;
My Catholic Faith, A Manual of Religion, page 135, 1963, My Mission House, Kenosha, Wisconsin
Actually only those are to be included as
members of the Church who have been baptized and profess the true faith, and who have not been so unfortunate as to separate themselves from the unity of the Body, or been excluded by legitimate authority for grave faults committed.
Mystici Corporis Christi, par. 22