Section 508 of the Rehabilitation Act (United States) requires WCAG Level AA conformance for electronic documents.
The US Section 508 standards cover accessibility requirements for the federal procurement of electronic content.
Prior to the refresh of these standards in 2017, meeting the accessibility requirements required following a specific set of guidelines set out in the legislation. With the refresh, conformance of electronic content is now aligned with meeting WCAG Level AA.
The conformance requirements for electronic content now read as follows:
E205.4 Accessibility Standard. Electronic content shall conform to Level A and Level AA Success Criteria and Conformance Requirements in WCAG 2.0 (incorporated by reference, see 702.10.1).
EXCEPTION: Non-Web documents shall not be required to conform to the following four WCAG 2.0 Success Criteria: 2.4.1 Bypass Blocks, 2.4.5 Multiple Ways, 3.2.3 Consistent Navigation, and 3.2.4 Consistent Identification.
E205.4.1 Word Substitution when Applying WCAG to Non-Web Documents. For non-Web documents, wherever the term "Web page" or "page" appears in WCAG 2.0 Level A and AA Success Criteria and Conformance Requirements, the term "document" shall be substituted for the terms "Web page" and "page". In addition, in Success Criterion in 1.4.2, the phrase "in a document" shall be substituted for the phrase "on a Web page".
These requirements closely reflect the interpretation of WCAG conformance in the EPUB Accessibility specification. A document that conforms to the EPUB Accessibility specification, meeting WCAG Level AA, will conform to section 508 (the reverse is not true, however, as the EPUB specification has additional requirements for conformance).