Complex sentence: A landmark decision differs from a "cause célèbre" in that a case that draws public attention may not involve any substantial changes to the law or creation of new law, conversely a landmark decision may not impinge upon the consciousness of the general public.
Split into simpler sentences: A landmark decision differs from a "cause célèbre" in that a case that draws public attention may not involve any substantial changes to the law or creation of new law. Conversely, a landmark decision may not impinge upon the consciousness of the general public.