The AAAS has now put on-line a list of all its members since its founding, searchable by subject.  The omissions in the "Law" category are just breathtaking–they include such giants of law and legal scholarship in the 20th-century as Karl Llewellyn, Leon Green, Jerome Frank, Milton Handler, William O. Douglas, W. Page Keeton, John Henry Wigmore, and William Prosser.  (Antipathy towards legal realists seems to be playing a role here, though doesn't explain all the omissions.)  This is probably a worse track record of misses than even the Nobel Prize in Literature's!

ADDENDUM:  Larry Garvin (Ohio State) identifies some other surprising omissions:  Robert Jackson, Louis Brandeis, Arthur Corbin, Allan Farnsworth, Thurman Arnold, Max Radin, Charles Warren.