BSA_en_tn/act/15/21.md

Moses has been proclaimed in every city ... and he is read in the synagogues every Sabbath

James is implying that Gentiles know how important these rules are because Jews preach them in every city where there is a synagogue. It also implies the Gentiles can go to the teachers from the synagogues to learn more about these rules. (See: rc://en/ta/man/translate/figs-explicit)

Moses has been proclaimed

Here "Moses" represents the law of Moses. This can be stated in active form. Alternate translation: "The law of Moses has been proclaimed" or "Jews have taught the law of Moses" (See: rc://en/ta/man/translate/figs-metonymy and rc://en/ta/man/translate/figs-activepassive)

in every city

The word "every" here is a generalization. Alternate translation: "in many cities" (See: rc://en/ta/man/translate/figs-hyperbole)

and he is read

Here "he" refers to Moses, whose name here represents his law. Alternate translation: "and the law is read" or "and they read the law" (See: rc://en/ta/man/translate/figs-metonymy)