Tinok shenishba. Some poskim give modern-day secular Jews the status of “tinokos shenishbu” (דינו מבואר ברמב''ם פ''ג ממרים ה''ג ). Meaning, since they grew up in a secular environment and their parents and teachers did not raise them with Torah, they did not have a choice. Their minds were taken captive and they do not know anything better than a secular lifestyle, as they were not exposed to Torah and mitzvos, like a child captive who was not exposed to the Torah way of life. If so, perhaps they do not have mumar status even if they are publicly mechallel Shabbos ל"ע (שו''ת בנין ציון החדשות סי' כ''ג ). This has ramifications for multiple halachos, e.g., yayin nesech, testimony, and the like. Some poskim are meikel with respect to their status (שו''ת מלמד להועיל או''ח סי' כ''ט, חזו''א הל' עירובין סי' פ''ז אות י''ד, חלקת בנימין סי' קי''ב ד''ה עממים ).
Not considered tinok shenishba. Secular Jews today are, generally speaking, exposed to Jewish life by Torah observant Jews who live near them. Similarly, all the information in the world is available to anyone who wants. One can get information on any halacha, minhag, or Torah source within seconds. Hence, every secular Jew can easily be exposed to Yiddishkeit if he wanted to. If he remains in his ways, it is simply because he desires to. For this reason, several poskim hold that according to halacha, most secular Jews today do not have the status of tinokos shenishbu and default back to a mumar status(מרן בעל שבט הלוי, הגריש''א , תשובות והנהגות ח''א סי' ת''ע ).
Nevertheless, some poskim hold that a Jew who was born secular retains the status of a tinok shenishba and is not considered a mumar. To internalize Torah and experience its truth, one must learn from a teacher and role model who can explain and implant the truth of our holy Torah, transforming it into a living Torah, not just lifeless information. Simply being exposed to knowledge as mere information is not enough to internalize the Torah and its ways to the point that one would be guilty of intentionally not keeping the Torah (הגר''י זילברשטיין ועוד ).
Off the derech OTD. A person who is “off the derech” ל"ע and publicly mechallel Shabbos has the status of a Jewish mumar (above, 12 and on), as he knows the Torah and is just going through a temporary crisis and making bad choices. Thus, during this time, even if he visits his family, the halachos of bishul akum should l’chatchila be kept [may Hashem illuminate the path for them so they all swiftly return with sincere teshuva].
