ELS = Empirical Legal Studies.
CLS = Criticial Legal Studies.
I found that via the Empirical Legal Studies blog, which declines to offer any comment other than "Interesting." Okay. Nothing like defending yourself. Here's what I think: Academics have an interest in getting people to believe that what they do is central. Others — others who don't provide them with reinforcement and admiration — are over there, out of the mainstream — mysterious and disconnected.
Italics = Leiter's words or derivations from Leiter's words.
The ELS scholars mean to put themselves at the center and thereby make Leiter seem mysterious and disconnected, even as he would do that to them.