Is there any Bi-law that protects Nurses from continually being mandated for those hiibutial call outs?
That will vary state by state. You will need to find out what the laws are for your state.
In mine, mandating for unseen emergencies, declared state of emergency, and where relieving the nurse would interfere with the level of care provided (as long as that care is already in progress, such as a procedure or surgery), are permitted. However, the use of mandated overtime for chronic short staffing is not allowed.
Again, please seek information from your state BON website and your state Department of Labor website.