Starting June 21, creating and distributing video game hacks will be illegal in South Korea.
According to GameToc (via tipster Sang), the law was passed last December and goes into effect later this month. It not only specifically mentions "game hacks," but it also makes creating and distributing private servers illegal.
It's not exactly clear how this applies to certain mods, but the point of the law appears to be targeting hacks that negatively impact games.
Those found guilty of breaking this new regulation can be fined up to the equivalent of $US50,000 ($66,221) or be sentenced to up five years in prison. Tipster Sang notes that the law does not have a clear written clause regarding users but broadly states "not to perform acts that disturb the game distribution process or rules."