How can they not be?

Here is what I mean: Paul writes,

For circumcision indeed is of value if you obey the law, but if you break the law, your circumcision becomes uncircumcision. So, if a man who is uncircumcised keeps the precepts of the law, will not his uncircumcision be regarded as circumcision? Then he who is physically uncircumcised but keeps the law will condemn you who have the written code and circumcision but break the law.

So do we have examples of this actually happening?  Before the Law was given (though it related to a law actually repeated by Moses in Deuteronomy):

Then Judah identified them and said, “She is more righteous than I, since I did not give her to my son Shelah.” And he did not know her again.

And then after the Law is given, Jesus recalls:

And he said, “Truly, I say to you, no prophet is acceptable in his hometown. But in truth, I tell you, there were many widows in Israel in the days of Elijah, when the heavens were shut up three years and six months, and a great famine came over all the land, and Elijah was sent to none of them but only to Zarephath, in the land of Sidon, to a woman who was a widow. And there were many lepers in Israel in the time of the prophet Elisha, and none of them was cleansed, but only Naaman the Syrian.”

One notes that the widow was shown to be exemplary in her faith.  Naaman too compares favorably to the king of Israel:

So he went, taking with him ten talents of silver, six thousand shekels of gold, and ten changes of clothing. And he brought the letter to the king of Israel, which read, “When this letter reaches you, know that I have sent to you Naaman my servant, that you may cure him of his leprosy.” And when the king of Israel read the letter, he tore his clothes and said, “Am I God, to kill and to make alive, that this man sends word to me to cure a man of his leprosy? Only consider, and see how he is seeking a quarrel with me.” But when Elisha the man of God heard that the king of Israel had torn his clothes, he sent to the king, saying, “Why have you torn your clothes? Let him come now to me, that he may know that there is a prophet in Israel.”

Also Jesus referred to the Ninevites and the Queen of Sheba as specifically condemning Jews:

The men of Nineveh will rise up at the judgment with this generation and condemn it, for they repented at the preaching of Jonah, and behold, something greater than Jonah is here. The queen of the South will rise up at the judgment with this generation and condemn it, for she came from the ends of the earth to hear the wisdom of Solomon, and behold, something greater than Solomon is here.

Also we read in Luke 17 of Jesus comparing a Gentile favorably in comparison to Jews:

On the way to Jerusalem he was passing along between Samaria and Galilee. And as he entered a village, he was met by ten lepers, who stood at a distance and lifted up their voices, saying, “Jesus, Master, have mercy on us.” When he saw them he said to them, “Go and show yourselves to the priests.” And as they went they were cleansed. Then one of them, when he saw that he was healed, turned back, praising God with a loud voice; and he fell on his face at Jesus’ feet, giving him thanks. Now he was a Samaritan. Then Jesus answered, “Were not ten cleansed? Where are the nine? Was no one found to return and give praise to God except this foreigner?” And he said to him, “Rise and go your way; your faith has made you well.”

And also this from Matthew 8:

When he entered Capernaum, a centurion came forward to him, appealing to him, “Lord, my servant is lying paralyzed at home, suffering terribly.” And he said to him, “I will come and heal him.” But the centurion replied, “Lord, I am not worthy to have you come under my roof, but only say the word, and my servant will be healed. For I too am a man under authority, with soldiers under me. And I say to one, ‘Go,’ and he goes, and to another, ‘Come,’ and he comes, and to my servant, ‘Do this,’ and he does it.” When Jesus heard this, he marveled and said to those who followed him, “Truly, I tell you, with no one in Israel have I found such faith. I tell you, many will come from east and west and recline at table with Abraham, Isaac, and Jacob in the kingdom of heaven, while the sons of the kingdom will be thrown into the outer darkness. In that place there will be weeping and gnashing of teeth.” And to the centurion Jesus said, “Go; let it be done for you as you have believed.” And the servant was healed at that very moment.

In this case, though the centurion was not under the Mosaic Law as such, his behavior toward the people of the Mosaic Covenant gained him a good testimony from the Jews themselves.  In the parallel account in Luke 7 we read,

Now a centurion had a servant who was sick and at the point of death, who was highly valued by him. When the centurion heard about Jesus, he sent to him elders of the Jews, asking him to come and heal his servant. And when they came to Jesus, they pleaded with him earnestly, saying, “He is worthy to have you do this for him, for he loves our nation, and he is the one who built us our synagogue.”

So we have several instances of Jews being condemned in comparison to Gentiles.  And what they all have in common is that in no case whatsoever were these Gentiles operating by “general revelation.”  In each case they were responding to special revelation.  I consider this further evidence that Romans 1.18ff is not about how Gentiles are operating in the environment of “natural revelation” but rather how they are acting in the wake of the post-exilic migration of Jews all over the Mediterranean world.  It is also evidence that Romans 2.14 is commonly mistranslated.  It should not be

For when Gentiles, who do not have the law, by nature do what the law requires, they are a law to themselves, even though they do not have the law.

But rather

For when Gentiles, who do not have the law by nature, do what the law requires, they are a law to themselves, even though they do not have the law.