1360: 34 Edward 3 c.1: What sort of persons shall be justices of peace; and what authority they shall have.
FIRST, That in every county of England shall be assigned for the keeping of the peace, one lord, and with him three or four of the most worthy in the county, with some learned in the law,
(2) and they shall have power to restrain the offenders, rioters, and all other barators, and to pursue, arrest, take, and chastise them according to their trespass or offence;
(3) and to cause them to be imprisoned and duly punished according to the law and customs of the realm, and according to that which to them shall seem best to do by their discretions and good advisement;
(4) and also to inform them, and to inquire of all those that have been pillors and robbers in all the parts beyond the sea, and be now come again, and go wandering, and will not labour as they were wont in times past,
(5) and to take and arrest all those that they may find by indictment, or by suspicion, and to put them in prison;
(6) and to take of all them that be not of good fame, where they shall be found, sufficient surety and mainprise of their good behaviour towards the King and his people, and the other duly to punish, to the intent that the people be not by such rioters or rebels troubled nor endamaged, nor the peace blemished, nor merchants nor other passing by the highways of the realm disturbed, nor put in the peril which may happen of such offenders.
(7) And also to hear and determine at the King’s suit all manner of felonies and trespasses done in the same county, according to the laws and Customs aforesaid:
(8) and that writs of Oyer and Determiner be granted according to the statutes thereof made, and that the justices which shall be thereto assigned be named by the court, and not by the party.
(9) And the King will, that all general inquiries before this time granted within any seignories, for the mischiefs and oppressions which have been done to the people by such inquiries, shall cease utterly and be repealed;
(10) and that fines, which are to be made before justices for a trespass done by any person, be reasonable and just, having regard to the quantity of the trespass, and the causes for which they be made.
Further reading: Wikipedia.