In that sense that they should have the God’s law written in their heart, as promised in the Deuteronomy 30:6-9 and Jeremiah 31:31-34. By what the Bible tells in these scriptures, it would mean person is a Jew. But, as you might know, not all agree with this, but, in any case, this is what the Bible tells, people are free to believe something else, if they want.
For he is not a Jew who is one outwardly, neither is that circumcision which is outward in the flesh; but he is a Jew who is one inwardly, and circumcision is that of the heart, in the spirit not in the letter; whose praise is not from men, but from God.
Romans 2:28-29
But if some of the branches were broken off, and you, being a wild olive, were grafted in among them, and became partaker with them of the root and of the richness of the olive tree; don't boast over the branches. But if you boast, it is not you who support the root, but the root supports you. You will say then, "Branches were broken off, that I might be grafted in." True; by their unbelief they were broken off, and you stand by your faith. Don't be conceited, but fear; for if God didn't spare the natural branches, neither will he spare you.
Romans 11:17-21
And that can happen through the words Jesus declared. His words can cause change in persons mind so that he becomes righteous, which means person has the wisdom of the just and person wants to do what is right and good.
But as many as received him, to them he gave the right to become God's children, to those who believe in his name: who were born not of blood, nor of the will of the flesh, nor of the will of man, but of God.
John 1:12-13
It is the spirit who gives life. The flesh profits nothing. The words that I speak to you are spirit, and are life.
John 6:63
… Whoever is born of God doesn't commit sin, because his seed remains in him; and he can't sin, because he is born of God. In this the children of God are revealed, and the children of the devil. Whoever doesn't do righteousness is not of God, neither is he who doesn't love his brother.
1 John 3:7-10
And that means to be “born anew”.
… "Most assuredly, I tell you, unless one is born anew, he can't see the Kingdom of God." Nicodemus said to him, "How can a man be born when he is old? Can he enter a second time into his mother's womb, and be born?" Jesus answered, "Most assuredly I tell you, unless one is born of water and spirit, he can't enter into the Kingdom of God! That which is born of the flesh is flesh. That which is born of the Spirit is spirit. Don't marvel that I said to you, 'You must be born anew.'
John 3:3-7
When person is born anew by the words Jesus declared, he has the law written in his heart and then he has the correct understanding and wants to do what is right in God’s eyes. And that is why I believe eternal life is promised only for righteous, they want to do what is good and right.
These will go away into eternal punishment, but the righteous into eternal life.
Mat. 25:46
For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
Romans 6:23