halacha - Can a Jew lose their Jewish Status?

Can a Jew lose their status as being a Jew by performing any action (example: performing idolatry, disavowing core beliefs, converting to another religion, etc)? Or once a person is a Jew then they keep this status no matter what?

And if a person would always maintain their status as a Jew (in terms of other Jews viewing that person to still be obligated to follow the commandments), then what in practice would be the significance of a Jew converting to another religion?

Answer

For a person who has renounced their Judaism, it appears that while the person doesn't need to undergo a full conversion (on a Torah level), they do need to reaccept the Torah on some level and immerse in a mikvah before returning to the previous status. This seems to be especially true if the Jew literally worshiped idolatry.

1. Rambam, Hil. Mamrim 3:1-3: A person who doesn't believe in the Oral Torah, of his own will (ie: he was not mislead by someone) is no longer part of Israel - "כל אלו אינן בכלל ישראל"


2. Rambam, Hil. Avodah Zarah 2:5: A Jew who worships idolatry is like a non-Jew in all respects - ישראל שעבד עבודה זרה--הרי הוא כגוי לכל דבר


3. Shulchan Aruch Yoreh Deiah 268:12, Rema: A Jewish apostate who performs Teshuvah (repents) does not need to immerse in a mikvah (in order to return to his former status, on a Torah level); on a rabbinic level he has to immerse and accept upon himself the mizvot ("דברי חברות") in front of three people.

If the person converted to another religion, there may also be procedural differences depending on what religion the person converted to (since some religions may have the status of being idolatrous, and some may not), or what they specifically did to disown their Judaism (or what beliefs they held that were against Jewish core beliefs).

Of course, this is a complicated topic with additional responsa literature, so please see a proper rabbinic authority if this is a practical issue for you.

Further reading: