U.S. law and international standards: Section 508 and W3C
Accessibility policies vary from country to country, but most countries, including those in the European Union, have adopted standards based on the Web Content Accessibility Guidelines (WCAG) of the World Wide Web Consortium (W3C). In the United States, Section 508 of the U.S. Rehabilitation Act mandates that web content maintained by the federal government be made accessible to people with disabilities. This law is based on W3C Priority One checkpoints.
Adobe accessibility content often refers to Section 508. If you are working in another country or under different standards, be aware that Section 508 issues are, for the most part, parallel to W3C Priority One issues. While there are subtle differences between Section 508 and W3C Priority One and different approaches to implementing them, the checkpoints for each are very similar.