The Shulchan Aruch (Yoreh Deah 115:2) unequivocally rules in accordance with the ruling of the Rambam. The Rama adds that this is the accepted custom and warns against being “Poreitz Geder” breaking the fence enacted by Am Yisrael regarding this matter. The Rama adds, though, that an exception to this lenient ruling is a place where the Jewish community has a tradition to follow the lenient ruling of the Geonim of Narbonne. The Beit Yosef, on the other hand, is far less tolerant of those places that maintain their tradition to follow the lenient approach to this issue. He strongly urges those few communities who follow the lenient view to adopt the practice of the overwhelming majority of Jewish communities throughout the world to be strict about this matter.
The Chochmat Adam (53:38 and 67:7) and the Aruch Hashulchan (Y.D. 115:16-17) rule completely in accordance with the strict view and express harsh words against those who follow the lenient opinion. These authorities, writing in the nineteenth century, make no mention of communities that are lenient regarding this issue. It seems that by their time there were no longer any communities that followed the lenient tradition.
This is an especially relevant issue today, as cheese is made either from non-animals sources such as microbial rennet or animal sources that have been reduced to a powder, which seems to cause the stomach lining to lose its prohibited status as it has been reduced to “mere wood” (Rama Y.D. 87:10). Accordingly, the reason for this enactment is virtually never relevant today. Nonetheless, the prohibition still applies and all observant Jews strictly adhere to this prohibition.
