This is the first new essay commissioned on the subject in more than fifty years (the last one was by Julius Stone, also a legal realist!).  I had the privilege of co-authoring the new essay with a former student, the legal philosopher Michael Sevel (not a legal realist, but like Stone, at the University of Sydney!).  Other areas of philosophy in EB appear to be more current (e.g., philosophy of mind by Georges Rey, philosophy of language by Simon Blackburn, philosophy of science by Philip Kitcher).  Alas, you need to access it from an institution that subscribes to read this essay or any of the others in full.

UPDATE:  An editor at EB writes:  "in fact anyone can read the entire article for free if he/she comes to it through a Google search. I believe we are fourth or fifth in the hit list returned by searching on 'philosophy of law'. Clicking on the link should provide access to the full article. (Obviously, searching on "philosophy of law Britannica" would make it even easier.) Likewise any other article in Britannica."  Useful information, I didn't realize that!