It's all so obvious -- once someone has done it. Networks can be fitted to many things, including webs of ideas and legal opinions.
The Economist ("Statistical modelling: The wisdom of Hercules") reports on legal research by Prof. Seth Handler that involves plotting networks that link large numbers of Supreme Court decisions, in order to detect patterns of precedent. Webs and central nodes emerge.
The research shows, not surprisingly, that the legal landscape changes in the 20th century. Cited work by James Fowler and Sangick Jeon reveals that, " ... before the American Civil War, the most authoritative cases involved freedom of contract. After the war and until the 1930s, when Roosevelt's New Deal was enacted, these were replaced by cases dealing with balance of power to regulate commerce between Congress and the states. Finally, around the second world war, as the Supreme Court shifted its focus to civil liberties, the most important cases became those concerning freedom of speech. According to the model, civil rights opinions remain ascendant today."
Along the way, the reliance on precedent decisions, the analysis shows, experienced a "precipitous drop." Yes, they do legislate from the bench.