This event is fired whenever potential mob griefing is about to occur. It has a result which determines whether the default behaviour occurs or not:

• allow: the griefing is allowed
• deny: the griefing is prevented
• default: the griefing occurs according to Vanilla logic.

You will need to cast the event in the function header as this class:
crafttweaker.event.MobGriefingEvent
You can, of course, also import the class before and use that name then.

MobGriefing Events implement the following interfaces and are able to call all of their methods/getters/setters as well:

• ILivingEvent
• IEventHasResult