Schedule board allowing bookings when resource is unavailable?

Hi all,

So.. Is this default functionality?
It seems strange that as a scheduler, I am able to add a booking to the schedule board (grayed out periods) which are outside of a resources work hours, in all variants of non-working hours: e.g. due to works hours observing configured business closures; outside of configured resource work hours; during approved time off periods etc.

If there is no functionality OOB to stop or alert the scheduler of the fact that they are attempting to book during a resources unavailability period, what is the alternative? Do I need to create a "booking rule" to facilitate this functionality? If so, does anyone have a guide, or reference I can use to work from? JScript for the web resource? Or am I just missing something here?

thank you in advance :)