magistrate

Short definition from Wiktionary

Noun

1. 1
   A judicial officer with limited authority to administer and enforce the law. A magistrate's court may have jurisdiction in civil or criminal cases, or both.
2. 2
   A high official of the state or a municipality in ancient Greece or Rome.
3. 3
   A comparable official in medieval or modern institutions.
4. 4
   A master's degree.