Yale Law School is starting a brand new degree called a Ph.D. in Law. This degree will be the first of its kind in the United States and will offer lawyers with JDs who want to enter academia the opportunity to focus on legal scholarship for another three (3) years. According to Yale's web site:
"This program will offer young scholars an opportunity to contribute to the development of law as an academic field, and it will provide an alternate path into law teaching alongside existing routes such as fellowships, advanced degrees in cognate fields, and transitioning directly from practice or clerkships."
Applications are already being accepted, and classes will begin in September of 2013.
For more information, read Yale's press release or Yale's report/study on the new degree.