WCAG 2.2
Web Content Accessibility Guidelines, version 2.2 — the accessibility standard that underlies most institutional and regulatory accessibility requirements for digital content.
WCAG 2.2 is published by the W3C's Web Accessibility Initiative. It organizes accessibility requirements into four principles: Perceivable, Operable, Understandable, Robust — and assigns each requirement a conformance level (A, AA, or AAA).
For event captioning specifically, the relevant criteria are 1.2.2 (Captions, Prerecorded — Level A) for recorded content and 1.2.4 (Captions, Live — Level AA) for live streaming. Both require synchronized, understandable captions for any video with audio.
WCAG 2.2 is the basis for ADA Title III enforcement guidance in the US, EN 301 549 in the EU, and most institutional policies for higher education and government.