Rom 2:12 For as many as have sinned without law will also perish without law, and as many as have sinned in the law will be judged by the law
Rom 2:13 (for not the hearers of the law are just in the sight of God, but the doers of the law will be justified;
Rom 2:14 for when Gentiles, who do not have the law, by nature do the things in the law, these, although not having the law, are a law to themselves,
Rom 2:15 who show the work of the law written in their hearts, their conscience also bearing witness, and between themselves their thoughts accusing or else excusing them)
Paul contrasts two groups: those who are under the law and those who are not. Each group will be judged on different standards. The group under the law will be judged by the law, and the group not under the law has a separate law under which they will be judged. They are judged by conscience. Verse 6 reads that God will “WILL RENDER TO EACH ONE ACCORDING TO HIS DEEDS”.
What this shows is that God has different standards for different people. People are judged under a curve by how much they know and what upbringing they had. Even the gentiles, who didn’t have the law, are eligible for eternal life (verse 7).