By the way, it appears all sins keep people in the Catholic church, according to Campion.
Yes I can. And if you want to start a thread on that topic I will glad to contribute, but I’m not going to support your efforts to obfuscate on this thread about Martin Luther.
If you're going to mention a Freeper in a post, it's considered common courtesy to put them in the "To" list.
I would also appreciate it if you would not attempt to paraphrase what I said; it's easy enough to cut and paste the quotation or at least a reference to the post.
You seem to be using "excommunicate" as a synonym for "remove". That isn't quite correct.
A Catholic who is excommunicated does not become a non-Catholic; he becomes a Catholic who is deprived of the right to receive the sacraments until such time as he repents of his evil. Typically this means that he needs to confess to a bishop.
(Priests may have the faculties to absolve from certain excommunicable offenses. Certain other offenses can only be absolved by the Pope.)
Specific latae sententiae excommunicable offenses are listed in canon law. Put "catholic canon law" into Google; it's online in several places.
The Pope cannot remove anyone from the Church. He doesn't have that power.
A person can remove themselves by a "formal defection" -- by joining another religion, or formally announcing (in a letter to their bishop, for example) that they are leaving the Church.
Even then, they have a different relationship to the Church than a non-Catholic does, because they can return simply by making a good confession.
The Catholic understanding of Catholic baptism in canon law is much like the Jewish understanding of being born of a Jewish mother in halacha. It can't really be un-done.