Question: Is it true that they are not allowed to call your parents if you are over 18 and were not caught drunk or in possession, even if you were in a house where they found empty beer containers and no parents?
Answer: 1. Can the police notify parents if a person over 18 is cited for alcohol?
The police have no obligation to contact a parent of an adult. If you were arrested at a party away from home, for example, you would be cited and released OR taken to jail, where you could call your parents if you want to, in order to ask them to post bond. However, police reports are generally public records. There is no legal reason why an officer would be in trouble for revealing the contents, though there is also no reason for the officer to notify them.
2. Can the police notify parents of an adult if the adult child is arrested at the parents' home?
Because the owners of the home are usually advised of criminal arrests that take place at their home, the police might notify the owners to ensure they would come to the scene to be certain the home was locked up safely. So if you were cited for alcohol at your parents' home, and you are not the listed owner of the home, the police might call your parents to tell them they need to come to the scene to lock up the house and to be sure there were no damages.