Scamming is not against server rules. I don't know how to make a new system to avoid scams. But IRL you get scammed when you send money to the Nigerians so I think it should be in the game. But, you can let cops arrest people and fine them like a lot of money for scamming. Maybe I'll make a court room in City Hall so cops can put them on trial or something lol.

Cops should not kill people for scams though, only arrest. (Unless of course they resist with guns...)