Between the Reformation and the Civil War, the crown and its ministers sought to ensure that the JPs who ran county governments would enforce religious policy. The composition of county commissions was adjusted to the religious complexion of the regime, so that justices were appointed or dismissed according to their opinions, Protestant or Catholic. There were some major purges under Edward VI, Mary and Elizabeth, and frequent instability, but there were constraints on the crown's ability to obtain compliance. Under James I, dismissals of JPs were sometimes motivated by official hostility to the more godly Protestants, while from 1617 to 1625 more clergy were nominated as JPs. Under Charles I, some critical of Arminian tendencies and fiscal policy were expelled from the commissions of the peace. The late 1630s saw a new development – JPs leaving the office voluntarily, which, it is argued here, was partly impelled by their religious convictions.