How is it that a non-Catholic can receive the sacrament of penance? Is there a specific church teaching which addresses this? And no, I'm not talking about Fr. Kramer's writings.
In Treatise 3, Book 2, Chapter 2, Article 3 (Reasons that Separate a Baptized Person from the Body of the Church), Thesis 26, Salaverri states the following in Sacrae Theologiae Summa:
"A heretic, apostate and schismatic by the fact itself; and a person excommunicated by legitimate authority are separated from the body of the Church."
In Paragraph 1052 under Thesis 26, he states the following in regards to the opinion of theologians:
"That formal and manifest heretics are not members of the body of the Church can well be said to be the unanimous opinion among Catholics."
In Paragraph 1056 under Thesis and titled "Doctrine of the Church", he states the following:
"Part 1 is implicitly defined by the Council of Florence in the Decree for the Jacobites: D 1351. But concerning heretics and apostates we deduce our doctrine also from the formula of faith of the 'Clemens Trinitas,' from canon 23 of Lateran Council II, and from the Bull of Pius IX 'Ineffabilis Deus': D 74, 718, 2804."
Part 1 is in reference to the first part of Thesis 26, which is "a heretic, apostate, and schismatic by the fact itself" (are separated from the Body of the Church).
If one is separated from the Body of the Church, then he is a non-Catholic. How a non-Catholic who was formerly Catholic receives the Sacrament of Penance is that he renounces his heresy in the Sacrament of Penance and follows the direction of the priest.