Law as a whole (both written and unwritten law) is a vast and complicated set of arrangements and actions wherein agents (like businessmen, individuals, companies, lawyers, judges, policemen, government agencies) act: e.g., obey or infringe, enforce, litigate, adjudicate, defend, compete, learn, adapt. All such behaviors form concurrently the legal system, with its sub systems like a judiciary system, an enforcement system, a supervisory system. Aggregate patterns result. To look at the legal system, or sub systems within the law, from a complexity viewpoint then would mean asking how it evolved and evolves, and this means examining in detail how individual agents’ behaviors together form aggregate outcomes and how these outcomes in turn influence the future individual behaviors as a result and so on, ad libitum.
Complexity in other words asks how individual behaviors might react to the patterns they together create, and, again, how these patterns and these individual behaviors would alter as a result. Complexity is interested in real-time multi-level dynamics, in individual and aggregate behaviors co-evolving.