In the wake of a defector group's anti-Pyongyang leaflet activities Monday night, the South Korean government reiterated that it cannot forcibly regulate the activity. 
 
A Unification Ministry official told reporters Tuesday that the government only learned about the activity after it was completed. 
 
The ministry is believed to have been informed by police after the "Fighters for a Free North Korea" sent balloons carrying some 100-thousand anti-Pyongyang leaflets across the border.
 
The ministry official said the campaign has to do with the right of expression and the government cannot enforce regulations against it.
 
But the official added the government intends to take necessary measures if the border campaign causes a clear threat to the safety of local residents. He said officials will continue to urge the civic group to make wise decisions. 
 
Around 20 Americans including officials from the U.S. Human Rights Foundation are also believed to have attended the balloon launch.