Shulchan Aruch Yore Deah 159:2 permits charging ribbis (interest) from a non-observant Jew (i.e one who is completely removed from the Jewish people).
Although such a Jew has the status of a Jew in virtually all other areas of halacha [see reference below]. What could be the reason(s) for this?
To AA: I found the passage where this is asserted in "Laws of Ribbis" , p.98, footnote 18
"YD 159:2 permits charging interest to a non-observant jew . Shach explains that this applies only to one who is completely removed from the Jewish people. Although such an individual has the status of a Jewish in virtually all other areas of Halacha, the laws of Ribbis differ [This is based on a Biblical verse.drr Taz 159:1 and 3]"