John Calvin on Romans 2:12

12. Whosoever have sinned without law, Ανόμως commonly means unlawfully, wickedly, lawlessly; but here, as it is evident from the context, it signifies to be without law. The adjective ἀνόμος is also used once in this sense in 1 Corinthians 9:21. — Ed. etc. In the former part of this section he assails the Gentiles; though no Moses was given them to publish and to ratify a law from the Lord, he yet denies this omission to be a reason why they deserved not the just sentence of death for their sins; as though he had said — that the knowledge of a written law was not necessary for the just condemnation of a sinner. See then what kind of advocacy they undertake, who through misplaced mercy, attempt, on the ground of ignorance, to exempt the nations who have not the light of the gospel from the judgment of God.

Whosoever have sinned under the law, etc. As the Gentiles, being led by the errors of their own reason, go headlong into ruin, so the Jews possess a law by which they are condemned; The word “condemned” would be better in the text than “judged;” it would then more plainly correspond with the former part, where the word “perished” is used: and that it means “condemned” is evident, for those who have “sinned” are the persons referred to. — Ed. for this sentence has been long ago pronounced,

“Cursed are all they who continue not in all its precepts.” (Deuteronomy 27:26.)

A worse condition then awaits the Jewish sinners, since their condemnation is already pronounced in their own law.