Running 5.0.16 NE on RHEL

A resource / location was created. We logged into the resource and defined a subset of users who were allowed to schedule it ( userA and userB ), under Preferences -> Calendar -> Invites -> Allow only the following ... userA userB .

When userC books that resource, and email is sent to userC's account stating:
"You are not allowed to schedule this calendar resource".

That is good, but the event is added to their personal calendar. There is no indication within their calendar that the resource is unavailable. Also, all invitees receive the invitation to the event for a location that is not available.

Is there a way to check for the availability of a resource prior to sending out the invitation? Can invites not go out if the resource is unavailable? Can userC's calendar reflect that the resource is NOT available? Is there a better way to handle restricted resources?