Those are the questions Scott Hafemann addressed in his seminar paper at the British New Testament Conference, and his proposed answer was fascinating. Essentially, he argued, we need to translate the passage slightly differently than has been traditional, and we need to see the parallels between 2:12-16 and 2:25-29. The Greek of verse 14 reads:
 

 
Literally, and with minimal punctuation, we might translate it like this:

For when the Gentiles not having the law by nature do the things of the law, these not having the law to/for themselves are a/the law.

 
Usually, the sentence is translated with phusei (by nature) applying to the doing of the law, and with heautois (to/for themselves) qualifying “they are a law”. Thus the ESV:

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.

 
Hafemann, however, proposes punctuating the sentence differently:

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

 
In this reading, the Gentiles in question are Gentile Christians who fulfil the requirement of the law - loving God, loving neighbour - by the power of the Spirit, as we will see later on in Romans 8. As Gentiles, they do not have the law “by nature”, or “for themselves”, but keep the law anyway, and this serves to judge the Jews, who do have the law but don’t keep it. (This, for Hafemann, is the meaning of the phrase “they are the law.”) As such, 2:14 is saying the same thing as 2:27. And, since 2:15 does not contain reflexives, it is perfectly legitimate to see the accusing and excusing in this verse as applying to others, and not to the Gentiles themselves.
 
The upshot of this, then, is that 2:12-16 and 2:25-29 are making parallel points in Paul’s argument, as follows:
 
1. Hearing the law (2:12-13) and being physically circumcised (2:25) are of no value unless the law is also kept. It is those who keep the law, whether ethnically Jewish or not, who are justified (2:12-13, 25-27).
2. Gentiles do not have the law by nature (2:14) and are uncircumcised in the flesh (2:25-27).
3. However, some Gentiles are circumcised in heart, by the Spirit (2:26, 29), and have the law written on their hearts (2:15).
4. Consequently, they fulfil the law, by the Spirit, and are justified (2:13, 15-16, 26).
5. As such, they effectively judge the Jews who break the law (2:15, 27).
 
I think that’s a really interesting proposal. What about you?