He sent several letters to people in America, including some lawmakers, asking their help in this matter. Apparently, S. Korean authories try to drag out the procedure of security checks for N. Korean defectors when they travel abroad, which could last more than a month. His request would be still rejected.
It is not as if they would have trouble keeping track of him. He will be in America and in company of so-called hardliners against N. Korea. What security problem does he have ? His background is patently well-known. I think that the authorities fear that his words will discredit current S. Korean policy toward N. Korea. It is even possible that Mr. Hwang could defect again to America, which would be a huge embarrassment to S. Korean government, not seen since the late Kim Hyong-Uk testified in the U.S. Congress against the then-president Park Chung-Hee.