Duplication

I had created a world that several of my friends played on. Eventually, they got mad that I had to get on for them to play, so I created a survival realm. Now there has been this duplication exploit going on that the two youngest in our server have abused. Now we had found out they had been duplicating and they got mad because we told them to trash the duplicated items. Once we had gone back on the server, our town was ravaged. They had duplicated TNT and exploded our town. Ofcourse, kicked them and reloaded a save, but now with the new update coming out, I want to start a new realm and invite everyone back. So how do I ban pistons from my world? Is there a command or something? pls help.