http://www.davidhjgay.com/audio-books/believers-under-the-law-of-christ/

Let me quote the verses:
For when Gentiles, who do not have the law, by nature do the things in the law, these, although not having the law, are a law to themselves, who show the work of the law written in their hearts, their conscience also bearing witness, and between themselves their thoughts accusing or else excusing them.
I wish to deal with two main views of the passage. First things first, however.