Emerging Technology from the arXiv

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How Network Science Is Changing Our Understanding of Law

The first network analysis of the entire body of European Community legislation reveals the pattern of links between laws and their resilience to change.

  • January 29, 2015

One of the more fascinating areas of science that has emerged in recent years is the study of networks and their application to everyday life. It turns out that many important properties of our world are governed by networks with very specific properties.

These networks are not random by any means. Instead, they are often connected in the now famous small world pattern in which any part of the network can be reached in a relatively small number of steps. These kinds of networks lie behind many natural phenomena such as earthquakes, epidemics and forest fires and are equally ubiquitous in social phenomena such as the spread of fashions, languages, and even wars.

So it should come as no surprise that the same kind of network should exist in the legal world. Today, Marios Koniaris and pals at the National Technical University of Athens in Greece show that the network of links between laws follows exactly the same pattern. They say their network approach provides a unique insight into the nature of the law, the way it has emerged and how changes may influence it in the future.

The work of Koniaris and co focuses entirely on the law associated with the European Union. They begin by pointing out that this legal network is different from many other types of networks in two important ways.

First, it consists of different types of nodes of varying importance. European law has three sources. The first and most important is the treaties between countries that established the EU. Next are the regulations and directives that are based on these treaties. Finally, there is the case law that has emerged from the Court of Justice, from international law and the general principles of law. Each of these sources forms a subnetwork in which nodes are linked together and also to other subnetworks.

The other important way in which this network differs from many others is that the nature of the links between nodes can vary as well. For example, nodes can be linked on a legal basis but may also be linked by citations. These differences must also be taken into account.

To study the nature of the resulting network, Koniaris and co have extracted all the documents from the European Community’s legal database dating back to 1951. This amounts to 250,000 documents embedded in a network of over a million edges.

The team studied each subsection of the network and found that all were small world networks in themselves. In practice, this indicates that nodes are most commonly linked to their neighbors creating clusters but that these are also linked on much larger scales. That’s how it becomes possible to move from one part of the network to another in a small number of steps. This also leads to a power law structure in which a few laws are highly influential.

Network theorists know that these kinds of networks have specific properties. One of them is that they are robust and still tend to function when nodes and edges are removed. That is important in a legal network because laws sometimes become invalidated or changed and an interesting question is whether the legal network will still function as a result.

Koniaris and co test this by removing nodes and edges from the network at random and see how well connected it remains. In general, they say the networks are highly resilient.

But there is also a caveat. In small world networks, a small number of nodes are highly connected and therefore hugely important. Removing these can cause significant problems. When nodes are removed at random, it is highly unlikely that any of these will be affected. But when they are, problems can ensue. Knowing which laws are highly connected is therefore important.

Koniaris and co have also studied how the network evolved over time. They do this by looking at the way the network has changed as new laws have been added. They say the main effect of these changes is that the number of links has increased faster than the number of nodes. The result is a steep increase in the density of links within the network over time.

The network can also be using for visualizing the nature of the legal world. It reveals clusters and related connections and can help legislators determine the effect of proposed changes. This could also help improve the effectiveness of legal information retrieval. “Our hypothesis is that the Legislation Network can be exploited for text retrieval, in the same manner as hyperlink graphs on the Web,” say Koniaris and co.

That’s interesting work which builds on previous studies of legal networks that have simply looked at the pattern of citations between documents. Taking account of the different nature of nodes and the links between them provides greater insight than has been possible before.

It also shows how network science is spreading to every corner of scientific and social research.

Ref: http://arxiv.org/abs/1501.05237 : Network Analysis In The Legal Domain: A Complex Model For European Union Legal Sources

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