As an educator, I have made all of my staff aware that in our state we may not deny any parent access to their child, unless we have a copy of a court order restricting said access. In such a case, knowingly ignoring that court order could not only jeopardize the safety of the child, it can (and likely will) jeopardize that individual's job.
Not against your requests, they violated a court order by allowing access. As @shortridge stated above, you need to contact your Council, to ensure something like this does not happen again.