From Academy Bylaws:
Article III, Section 1. Membership shall be by invitation of the Board of Governors. Invitations to active membership shall be limited to those persons active in the motion picture arts and sciences, or credited with screen achievements, or who have otherwise achieved distinction in such categories as documentary, literary, packaging, below the line and music in the motion picture arts and sciences and who, in the opinion of the Board, are qualified for membership.
To be considered for Members-at-Large membership, an individual must have a minimum of ten years experience as a representative in the fields listed above.
(c) have, in the judgment of the Review Committee, otherwise achieved unique distinction, earned special merit or made an outstanding contribution as a Representative.