This article starts off by going through a scenario with Mr A and Mrs A and Mr A is getting a divorce from her in order to achieve "happiness." He will achieve this happiness by marrying Mrs B because he has the right to do so. He did this same act before to another Mrs A, but she tragically comitted suicide because of the divorce.
Lewis continues on to talk about the laws of nature, and the laws of the nation. That is, to pursue happiness by all lawful means. That we may do as much as we want as long as it is within the laws that our forefathers have set before us. The laws of nature are whatever we feel is morally right, or morally wrong.
Lewis writes this article on the basis of natural law, and makes it clear that Mr A was only out to get what it was the he wanted. I feel as though these people should have followed what was right according to the law of God. We do not deserve anything, let along happiness, and yet God still provides for His people.