The Montagues and the Capulets caused more than three brawls that disturbed the city, to end this the king made a death penalty. He vowed to put death on anyone caught fighting within the city walls. In my opinion I don't think they should be sentenced to death if they didn't kill someone.

 But just for fighting they should at least be locked away for some time. Because if you send away the Montagues and Capulets that were fighting it will still get the brawl to stop without killing them. Like when Tybolt killed Mercertio in that cause I would agree with the king. But for just fighting they should be sent away like Romeo when killed Tybolt. If you send them away