The current state of law regarding ARIA accessibility required for websites is that there are guidelines and standards established by organizations such as the
World Wide Web Consortium (W3C) Web Design Accessibility Standards and the W3C Web Accessibility Inititiative which serve as the standard for accessibility on the web.

In terms of the law, the Americans with Disabilities Act (ADA) requires that all places of public accommodation, including websites , be accessible to individuals with disabilities. While the ADA does not specifically mention ARIA, the use of ARIA can help to make a website more accessible and meet the requirements of the ADA.

In terms of determining if a page is accessible, the W3C has established the Web Content Accessibility Guidelines (WCAG) as the standard for web accessibility. The WCAG provides a set of success criteria for accessibility, and a page can be considered accessible if it meets all of the criteria. The WCAG is organized into three levels of conformance: A, AA, and AAA, with each level providing increasing levels of accessibility.

In summary, the current state of law regarding ARIA accessibility for websites is governed by guidelines and standards established by organizations such as the W3C and the WAI, and is influenced by the ADA. The WCAG provides a metric for determining if a page is accessible, and a page is considered accessible if it meets all of the success criteria.