I applaud the start of the http://universalcitation.org/ initiative but would urge those involves to not limit their purvue to just caselaw.
A full picture of the law at any point in time requires not just caselaw but also statutes, session laws and regulations to name but three. Relevant here is Joe Carmel's http://legislink.org/ initiative.
Law is a wonderful example of a domain where standards for citation are at least as important as standards for formats of the documents themselves.
The last 20 years are littered with failed initiatives to standardize the formats for all the document types relevant to law. Universal standard (semantic) formats for legal documents is a wonderful target to aim for but a tremendous amount of value can be unlocked by the significantly less daunting challenge of a universal citation framework.
In KLISS, we use the phrase "no wrong door" to describe the idea that any legal asset (a bill, a statute section, a journal, an attorney general opinion, a regulation, a court judgement etc.) that has cross-references *should* be traversable by machine. Moreover, to do this properly the linkages ahould be such that retrieving new documents by following links, retrieve the assets as they were at the time the originating document was created.
Anything short of that results in an incomplete (or worse, false!) view of the overall legal synoptics involved.