We know as well that God desires all to be saved (Acts 10:35, 1 Tim. 2:4) and that he judges non-Christian Gentiles according to the light they receive and how they, in conscience, respond to it:
"All who sin outside the law will also perish without reference to it, and all who sin under the law will be judged in accordance with it. For it is not those who hear the law who are just in the sight of God; rather, those who observe the law will be justified. For when the Gentiles who do not have the law by nature observe the prescriptions of the law, they are a law for themselves even though they do not have the law. They show that the demands of the law are written in their hearts, while their conscience also bears witness and their conflicting thoughts accuse or even defend them on the day when . . . God will judge people’s hidden works through Jesus Christ" (Rom. 2:12-15).
Paul says here that the Gentiles’ "conflicting thoughts accuse or defend them" before God, and he goes on to note that "those who are physically uncircumcised but carry out the law will pass judgment" on those who have the law but transgress it (Rom. 2:27).
These statements, together with Paul’s observation in Romans 2:14 ("For when the Gentiles who do not have the law by nature observe the prescriptions of the law . . ."), imply non-Christian Gentiles are, by God’s grace, in some way capable of observing the law, and, therefore, in some way capable of being justified through Christ (Rom. 2:10, 13).
The statement that the Gentiles who observe the prescriptions of the law show "the demands of the law are written in their hearts" (Rom. 2:14) is based on Jeremiah 31:33, which speaks of God writing his law in the hearts of the Israelites. That this is applied to non-Christian Gentiles means that they, too, are in some way part of God’s people.