EN 301 549
EN 301 549 is the harmonised European standard for the accessibility of ICT products and services; for websites and mobile applications it points in substance to the WCAG success criteria at level AA.
In practice
Meeting EN 301 549 counts in law as compliance with the European Accessibility Act and with the Austrian Accessibility Act (BaFG). The standard is therefore the technical link between abstract legislation and the WCAG criteria you can actually implement.