In ancient British customs, Conservators of the Peace (Latin: Custodes pacis), or Wardens of the Peace, were individuals who had a special charge, by virtue of their office, to see that the King's peace was kept.
Until the creation of the Justices of the Peace by King Edward III, there were several people, who by common law were interested in keeping the same—some having that charge as incident to other offices; others simply, or of itself, called custodes, or Conservators of the Peace.
More recently, the Chamberlain of Chester was a Conservator in the county of Cheshire; and petty constables are, by the common law, conservators in the first sense.
The Conservator of the Peace title is still used in the USA. For example, in Virginia, Special Conservators of the Peace have all the powers of a peace officer or law enforcement and are authorized to perform arrests, carry firearms as part of their duties, direct traffic, use a police logo on their uniform and utilize police style lights on their vehicles. They operate on public property such as court houses, parks and open spaces, housing developments, etc.