This category of police are the first of the dependent-class known as Ex-Officio. This simply means that they do not exist of their own authority. The source authority lies in Constables.
That means that anything that happens to Constables affects all Municipal Police, but not the other way around. The jurisdiction for a Municipal agency is confined to a specific community with some exceptions. Municipal officers are career officers and not elected.
Please see the Development page to further explain this. https://papolicealliance.org/history-of-police-in-pennsylvania/
In order to see the enabling legislation, and how it relates to Constables, please review the Agency Comparison file.