I highly doubt Lewis ever read C.F.W. Walther's The Proper Distinction Between the Law and the Gospel. But that really is neither here nor there. There undoubtedly is a wealth of study and writing to be done on the topic: C.S. Lewis on Law and Gospel. Thanks to Rev. Peters at his blog Pastoral Meanderings, there is another great article on the salient teaching of Law and Gospel as well as the insightful thoughts of Lewis on the same. Someday I hope to add to the wealth of information. But for this evening, enjoy the following link
C.S. Lewis on Law and Gospel.