  How do complex social systems evolve in the modern world? This question lies
at the heart of social physics, and network analysis has proven critical in
providing answers to it. In recent years, network analysis has also been used
to gain a quantitative understanding of law as a complex adaptive system, but
most research has focused on legal documents of a single type, and there exists
no unified framework for quantitative legal document analysis using network
analytical tools. Against this background, we present a comprehensive framework
for analyzing legal documents as multi-dimensional, dynamic document networks.
We demonstrate the utility of this framework by applying it to an original
dataset of statutes and regulations from two different countries, the United
States and Germany, spanning more than twenty years (1998-2019). Our framework
provides tools for assessing the size and connectivity of the legal system as
viewed through the lens of specific document collections as well as for
tracking the evolution of individual legal documents over time. Implementing
the framework for our dataset, we find that at the federal level, the United
States legal system is increasingly dominated by regulations, whereas the
German legal system remains governed by statutes. This holds regardless of
whether we measure the systems at the macro, the meso, or the micro level.
