What can the ECB do?

That's the question which needs an answer. So they're launching a "project to investigate the potential of a digital euro", and that's fine, but do they have the right to go further? When the ECB was created, I doubt there was anything in its mandate allowing it to create a digital currency. I guess it would require all eurozone members to agree on the project with the same terms and without conditions. I'm not expecting that anytime soon.