First of all — try talking to that person. Good communication quite often can solve a lot of problems. If that does not help and someone in the drawing spoils fun for everyone, you can prevent them from drawing altogether:
Make sure you're the admin of the drawing
Open the drawing Admin menu and change Own layers and Add/remove layer settings from "All" to "Approved". Warning: this will prevent everyone else from drawing as well. Make sure you follow the next steps as well.
Click on the trouble maker's avatar and then click on "Kick from all layers". They won't be able to rejoin a layer.
Change all other people's roles to “Approved”, so that they can continue to create and join layers.
