en_tn/rom/02/15.md

By this they show

"By naturally obeying the law they show"

the actions required by the law are written in their hearts

You can translate this in an active form. AT: "God has written on their hearts what the law requires them to do" or "God has shown them what the law requires" (See: rc://en/ta/man/translate/figs-activepassive)

bears witness to them, and their own thoughts either accuse or defend them to themselves

Here "bears witness" refers to the knowledge they gain from the law that God has written in their hearts. AT: "tells them if they are disobeying or obeying God's law" (See: rc://en/ta/man/translate/figs-idiom)

on the day when God will judge

This finishes Paul's thought from Romans 2:13. "This will happen when God judges"