1.2: Furious at yet another Montague-Capulet brawl disturbing the peace, the Prince orders that from now on, anyone who fights in public will be put to death.
3.1: Despite his warning, the Prince discovers that the Montagues and Capulets have been fighting again. This time, two young men are dead – and one of them is the Prince's cousin, Mercutio. "My blood for your rude brawls doth lie a-bleeding," he says (3.1.199). The Prince rules that, since Tybalt started the fight and killed Mercutio, there are extenuating circumstances for Romeo's killing Tybalt. So the Prince condemns Romeo to banishment rather than death.
5.2: The Prince comes into the Capulet tomb and finds Romeo and Juliet lying dead in each other's arms. He pronounces that the tragic deaths of the two lovers are a punishment for the hatred that the Montague and Capulet families have allowed to flourish. In the matter of Romeo and Juliet's death, the Prince rules, "Some shall be pardoned and some punished" (5.3.319). He suggests that the Friar will be pardoned; the fate of the Nurse and other participants is unclear. At the same time, the Prince says, the pitiful deaths of Romeo and Juliet are themselves a heavy burden that everyone must bear. In that sense, he says, "All are punished" (5.3.305).