It's the only piece of legal writing of his that's been found, so far. Even that was the subject of some pretty fancy footwork on the part of the campaign staff -- which, as Smith notes, had told everyone that as the Review's President, Barack "didn't write articles, he edited and reviewed them."
Yes, well, given the Review's publication schedule (at least at the time), this was written in around August of 1989, published in November of '89, and Barack became President in February of 1990.
The case comment discusses Stallman v. Youngquist, an Illinois case that declined to find a cause of action against mothers for mothers for the unintentional infliction of injuries to their infants before their birth.
In Smith's piece, legal scholars note the "moderation" of the language in the comment. Well, given the Review's editing process it would have gone through -- it's written, then the supervising editor edits it, then the president looks at it, then the executive editor edits it, and then it's printed -- that doesn't really reveal much.