Romans 13-16: Judgment comes from within.

Verse 13: Our actions speak louder than words, and when we act as we understand, then we are considered just.  Not just reading about it or talking about or even believing it really matters, but doing “it” is what makes us just (fair-minded, unbiased).

Verse 14-15: It says here that when the “Gentiles” [being interpreted as a Pagan, non-believer, or heathen] who do not read or have the “law” (law being the Christian Religion, Jewish Religion, rules set forth in the Bible) but still have it in their nature to DO the important things of the law, THEY THEMSELVES ARE the law for themselves.  They do the “law” because it is in their heart and their own conscience accuses or excuses themselves, within themselves [by their nature]. These “heathens” already have this internal judge.  And according to verse 13, these heathen are just over the religious person who does not do the “law”.

Verse 16: And when we have this law in our hearts our secrets are judged by God through Christ in you [the hope of glory]. Where Christ being in you is from Colossians 1:27.   Our secrets are judged from within (Christ in your heart).

And what is the most important law we are supposed to do and not just read about?

Mathew 22:36-40 says the most important laws are about LOVE and loving others, and this love is the basis of all the laws.

How can the non-Gentiles naturally do this law of love as it says some Gentiles [heathen] naturally do?