Yesterday unification activist Ro Su-hui walked across the DMZ in sensational scenes which saw him handcuffed, roped up and arrested upon his first steps across the border. Moments earlier he had been given a hero’s send-off in a highly orchestrated move by Pyongyang which can only be described, for now, as a clear but unnecessary propaganda victory.  With Ro now likely to face lengthy detention for his unauthorized visit, his arrest and case will continue to serve North Korean propaganda purposes in the months to come.  But the arrest once again underscores the controversial nature of South Korea’s National Security Law