Denying access to children can cause devastation to the lives of the parents denied and the children themselves. Introduce official safeguarding procedures, involving professional recommendations for this to happen. It should not be possible to deny access without these recommendations.
Too many parents are using their child/children as weapons by denying access to hurt the other parent. Not realising they are creating two victims. It can cause mental health issues including severe depression and anxiety. The parent denied the access feel powerless and more importantly, it's devastating to the wellbeing of children.