For example, firms issuing electronic money which is convertible to cash are required by law to secure funds equivalent to or more than the amount received from users, by making a security deposit or by other means.
As for developments overseas, in China, BigTech firms, including Alipay and WeChat Pay, that provide payment services are required to deposit funds equivalent to the amount received from their users in accounts at the People's Bank of China. This could be seen as an example of a scheme where BigTech firms issue private digital currencies based on the credibility of a central bank.