Under Complex Adaptive Systems, the central point is the agent, who are they, what they do, how they act, and how their actions shape the system. In International Law, it looks like complex adaptive systems. So the first question is who the agents are.
Those agents, from my personal point of view, should be the persons. In other words, people who have a go and relate to each other in different capacities caused the system of international law to emerge. Agents interact in various capacities: either as part of a university as professors or students; as researchers in ThinkTanks; as judges or arbitrators for different international courts and tribunals; as bureaucrats for various institutions. Their interactions cause the system to emerge.
However, a further point under complexity science is to understand the artifacts that those agents use as elements. Artifacts are, in essence, objects used by the agents. As explained by Axelrod and Cohen, those objects have specific characteristics that invite the agents to use them. For example, they can have a particular location, specific capability, and “affordances.”
As an artifact of international law, the Peace Palace has three elements: a particular location, a particular capability, and specific affordances. Its location is at The Hague, a city internationally recognized as a neutral place for resolving disputes. It is located in a home with a certain degree of neutrality that started more than a hundred years ago, as is explained by Maartje Abbenhuis. It also has a specific capability since the Peace Palace is home to different entities. On one side is the seat of the International Court of Justice (ICJ), also, for the Permanent Court of Arbitration (PCA), the Hague Academies, and the Peace Palace Library, just to name a few entities that are hosted there. In other words, it has a multipurpose capability.
Now, the last element listed is that of “affordances.” Axelrod and Cohen defined affordances as “Features that evoke certain behavior of agents.” (Harnessing Complexity p.6) And it appears that the Peace Palace may have such characteristics. It can be seen as a place that invites people to resolve their disputes peacefully. That is, it invites the agents to use the Peace Palace as an artifact for resolving disputes. If the agents of international law seek to resolve international disputes in such a place, then the Peace Palace is acting as an artifact of International Law. (I know this sounds like a circularity.) Like for example a “cup” for drinking something it invites you to drink, but not any type of drink, “coffee” it has the affordance to invite the agent to use it as a cup for drinking its coffee.