IDK…but my Douay-Rheims commentary says:
Ver 12. Whosoever have sinned without the law. That is, without the written law of Moses, against their reason and conscience, &c. And also those who being Jews, have sinned under this written law, shall be judged, even with greater severity, for having transgressed against the known law.
Ver 14-15 When the Gentiles…do by nature, or naturally, that is , without having received any written law, these men are a law to themselves, and have it written in their hearts, as to the existence of a God, and their reason tells them, that many sins are unlawful: they may also do some actions that are morally good, a by giving alms to relieve the poor, honouring their parents, &c. not that these actions, morally good, will suffice for their justification of themselves, or make them deserve a supernatural reward in the kingdom of heaven; but God, out of his infinite mercy, will give them some supernatural graces, by which they come to know, and believe, that he will reward their souls for eternity. Such, say S. Chrys. were the dispositions of Melchisedech, Job, Cornelius the Centurion, &c.
Not sure if this helps.