WolfPacking

The rule says that

• It is not allowed to abuse the position of Game Admin to get new allies into the game during an ongoing conflict with other active players. It is also forbidden to join a game just to get another country an excessive advantage or to damage another player/country

Ok, that's clear. But what if a player threatens me with an in game message of "having found a sworn enemy for all the next game to come", thus implying that he will join future games just to damage me? Can I report the message? There is room for some kind of punishment in a case like this?