Parents have the right to engage in the consumption of alcohol in a responsible and appropriate manner. However, alcohol is a substance that can have profound effects on behavior. When consumed often or in high quantities, it can severely affect people's ability to be good parents who are always looking out for their children's best interests.
It is common for one parent to have concerns about the behavior of another parent when child custody is shared. One might have reason to believe that the other parent is consuming alcohol while caring for their child, and the concerned parent will likely question the safety of their child.