Here are some "worked examples" of URN:lex identifiers, to act as a guide for those implementing URN:lex on their sites. Discussion of this topic is taking place here.
United States Code (per the Legal Information Institute):
For now, we are implementing US Code URNs inside <meta> tags, along the lines of the following example:
URN:lex is a proposed Internet standard for legal document identifiers written by Pierluigi Spinosa, Enrico Francesconi, and Caterina Lupo. It is intended to coexist with (and provide important infrastructure for) more semantically-laden approaches like LegisLink and Citability.
The following was written (by Dave Shetland and Tom Bruce) as a position statement for the Workshop on Legislative XML associated with the 2007 JURIX conference in Leiden:
The United States Code section number
[this is mostly a placeholder for now -- unedited notes follow]
Here's what we have in mind:
This example is the identifier for the majority opinion in NY Times v. Tasini.
It breaks into
-- the scheme oai_lii should be the same for all identifiers, everywhere, and
be associated with a series of standards documents and formal xml schemas.