Lava PvP in Mining

Lately, there has been a new fad where all the n00bies have been using lava to kill others, then in response, the ones killed lava the ones that lava'd them. Finally, both parties (hopefully) get banned. Perhaps we should make lava not able to be placed in mining? Or better yet, make it so that grays and yellows can't place it at all?

 

Yay! However, last night, some yellows were killing guests too, not sure how to deal with that.