Make the player be welcomed to the server and tell thim to not dm because this is not a dm server :D
They have the option to read the /rules. it automatically pops up when the register, if they choose to not read the /rules well that is their own fault. And they can always type /rules to read them at any time while they are in the server.
But still make it when the player joins it says Welcome PLAYERNAME to Enigmatic Cops And Robber. and some other stuff that would be useful for the player.
Maybe... I guess we will see what other players think.
I Think it's a pretty good idea :D
Like saw said all new players are forced to read the rules on registering but only 20%or so read the rules. Because we can skip to read them. So why not do like you most scroll through all the rules to unlock the close rules button on registration. The server sometimes send out random message that dm aren't allowed maybe that should come up more often, and last don't it tell you no dm when you are logging in?