CSRF The action you have requested is not allowed

I know about CSFR protection and I'm very happy that codeIgniter gives us this security mechanism.
But I still wonder what is the best way to handle this error?

You have to account for users that try to resubmit a form. Letting them run against this error wall is probably the worst experience for the user.

Instead there should be an appropriate error-page telling the user that the form was already submitted. but since this error is not a server error you can't catch it with an error controller or via routing (like for ex. a 404 page). or can you?

so how do you handle this? whats the best practice with codeIgniter?