Emerging Technology From the arXivJanuary 29, 2015

How Network Science Is Changing OurUnderstanding of LawThe first network analysis of the entire body of European Communitylegislation reveals the pattern of links between laws and their resilienceto change.

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

These networks are not random by any means. Instead, they are often connected in the now famoussmall world pattern in which any part of the network can be reached in a relatively small number ofsteps. These kinds of networks lie behind many natural phenomena such as earthquakes, epidemicsand 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 networkof links between laws follows exactly the same pattern. They say their network approach provides aunique insight into the nature of the law, the way it has emerged and how changes may influence it inthe future.

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

First, it consists of different types of nodes of varying importance. European law has three sources. Thefirst and most important is the treaties between countries that established the EU. Next are theregulations and directives that are based on these treaties. Finally, there is the case law that hasemerged from the Court of Justice, from international law and the general principles of law. Each ofthese 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 linksbetween nodes can vary as well. For example, nodes can be linked on a legal basis but may also belinked 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 theEuropean Communitys legal database dating back to 1951. This amounts to 250,000 documentsembedded in a network of over a million edges.

The team studied each subsection of the network and found that all were small world networks inthemselves. In practice, this indicates that nodes are most commonly linked to their neighbors creatingclusters but that these are also linked on much larger scales. Thats how it becomes possible to movefrom one part of the network to another in a small number of steps. This also leads to a power lawstructure in which a few laws are highly influential.

Network theorists know that these kinds of networks have specific properties. One of them is that theyare robust and still tend to function when nodes and edges are removed. That is important in a legalnetwork because laws sometimes become invalidated or changed and an interesting question iswhether 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 wellconnected it remains. In general, they say the networks are highly resilient.

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But there is also a caveat. In small world networks, a small number of nodes are highly connected andtherefore hugely important. Removing these can cause significant problems. When nodes are removedat 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 waythe network has changed as new laws have been added. They say the main effect of these changes isthat the number of links has increased faster than the number of nodes. The result is a steep increase inthe density of links within the network over time.

This densification process is likely to continue but it also suggests some interesting work for the future.Koniaris and co so the by looking at the pattern of evolution in the past, it may be possible to predictchanges in the future. For example, they hope to build a model that predicts where future links betweennodes will arise. And they plan to go even further. A more sophisticated approach will be to predictwhich legal documents will become amended or even invalidated, they say.

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

Thats interesting work which builds on previous studies of legal networks that have simply looked at thepattern of citations between documents. Taking account of the different nature of nodes and the linksbetween 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:arxiv.org/abs/1501.05237: Network Analysis In The Legal Domain: A Complex Model For EuropeanUnion Legal Sources

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