Wikilaw would be used to organize articles on legal concepts and legal decisions for legal research purposes.
Would incorporate the Wikisource legal documents, and would include more detailed versions of the Wikipedia articles on major legal cases and concepts, designed for use as a source in legal writings, and as a tool for learning about legal concepts and about the law. Would consist of sections for individual nations, as well as international organizations such as the EU and the United Nations, in order to be as inclusive as possible.
The Biggest Problem 
Among the problems that we face will be to get law students and lawyers to use Wikilaw as a resource. To accomplish this, we will need to prove that a wiki can be a viable legal research tool. It will be necessary to stop people from incorrectly changing pages for obscure legal concepts and decisions, but this is a problem for Wikipedia in general and it is handled sufficiently well there. And since I believe that many legal professionals with a comprehensive knowledge of the law would use Wikilaw, and Law Professors would encourage their students to participate in it, we would not lack eyes to catch those who might mess it up. Also, because there are many different interpretations of the law, articles would have to be written to include all reasonable perspectives, and not just the one considered valid by the writer. This is where Wikisource would be useful, as individuals wishing to advocate for a specific viewpoint of a legal principle could post their article on Wikisource, and provide a shorter discussion of their arguments in the Wikilaw article on the concept. Additionally, there is the variation of the law depending upon jurisdiction. It may be worthwhile to start in one jurisdiction - say state level courts in California.
Legal research is inherently difficult because there are so many different law journals and casebooks and not all of them are online in the same services, and most are not available to individuals not attending a law school or using the services of a good law library. A legal wiki would encourage law students, lawyers, law school professors, and laymen who are interested in the law, to contribute to a publicly maintained area for a summary of legal concepts and arguments, and encourage them to submit their own legal writings, and post publicly available legal records to Wikisource. By integrating Wikisource and Wikipedia, I believe a real resource for legal research could be developed by the wiki community for the benefit of all involved, just like Wikipedia.
Similar existing projects 
- JurisPedia, an encyclopædic project of academic initiative devoted to worldwide law, legal, and political sciences.
- World Wiki Encyclopedia of Law, a free encyclopedia of law.
- WikiLaw, a free law library that anyone can edit. The link goes to Jurispedia.
- American Wiki Legal Encyclopedia, the American Encyclopedia of Law, an encyclopædic project devoted to American law, with resources like legal abbreviations, legal thesaurus, legal dictonaries and some other tools.
- Wiki Law School, a legal-topic outline wiki aimed at law students as they prepare for final exams.