Hi Robert,
You can add this constraint in the entity access (access rules) of your registration entity. This will restrict the registrations a user can and will see in the (offline) app.
Hi Robert, I ended up resolving it like this: a before commit flow on the entity, where the user's account is retrieved and the association between the entity and account is set. And an XPath constraint on the User's access rule of the entity. Seems to work!