A roughly 70% solution is to mandate WCAG 2.1 AA conformance. After that the problems largely distill down to misleading and deceptive content. Deceptive content resulting in a financial harm not as a result of a technical defect is fraud.
How to prove fraud in court? Easy, make them liable for presenting accessibility conformance against the issue in question. The defendant only has to demonstrate a good faith effort to account for and correct the issue, but if they cannot do that, because fraud is intentional, take them to the cleaners.
How to prove fraud in court? Easy, make them liable for presenting accessibility conformance against the issue in question. The defendant only has to demonstrate a good faith effort to account for and correct the issue, but if they cannot do that, because fraud is intentional, take them to the cleaners.