Hi, CMatt.
Despite the fact that many CAF members over the years have misquoted Fr. Corapi, he has been very clear (I have heard many of his lectures multiple times on radio & TV) that, except by deliberate efforts in repudiation and self-identification, one never loses one’s Catholic identity. This is an important point theologically, because it means that one will be (according to the Church) judged at the end of one’s life within the framework of Catholic standards. One can be a totally non-practicing Catholic (used to be called “lapsed”), but you don’t become “Catholic” in quotes only; you become non-observant in that case, a non-observant, non-practicing Catholic. (no quotes)
1- A baptized Catholic can repudiate Catholicism passively, by not subscribing to its requirements: That repudiation is considered sin. (Abandonment of the faith.)
2- A baptized Catholic can repudiate Catholicism actively, by formally announcing one’s departure from the faith, such as writing to the bishop.
3- A baptized Catholic can repudiate Catholicism even more actively and more formally by embracing and formally entering into (by conversion) a different faith system, which usually involves ritual and some documentation.
Only #2 and #3 make a baptized Catholic “no longer Catholic.”