A TV screen shows a file image of US soldier Travis King during a news program at the Seoul Railway Station in Seoul, South Korea on July 24. (AP-Yonhap)

The story of a runaway US soldier to North Korea caught international attention last month, as he crossed the border a day after he was escorted to a South Korean airport to return to the US.

On July 17, Pvt. Travis King, 23, was on his way to Texas to face expulsion from the military after he had been jailed for nearly two months in South Korea for assault.

He was supposed to take a commercial flight from Incheon Airport to Fort Bliss in Dallas, Texas, but he walked out of the duty-free zone before the flight, as his escorts did not accompany him all the way to the boarding gate. With no eyes on him, he left the airport by telling local authorities he had lost his passport. The next day, he joined a tour to the Joint Security Area where he deliberately crossed the border.

The high-profile incident has not only raised security concerns for the Joint Security Area, but also highlighted an immigration loophole in South Korea due to its lack of immigration control authority over members of the United States Armed Forces stationed in the country.

Reports have raised questions that such a case could have been prevented if the private was escorted all the way to the departing flight or had been under authorities' watch in the airport, which is classified as the top security facility in Korea. But nothing could have been done as they were not informed of King's departure, the Ministry of Justice told The Korea Herald. It does not have authority to prevent cases similar to that of King from repeating without coordination with the United States Forces Korea, the ministry added.

King was facing disciplinary action in the US, having served a prison term for nearly two months -- instead of paying a fine of 5 million won ($3,800) -- after being convicted of damaging a police car in February. He potentially faced another criminal charge of inflicting physical violence on a 23-year-old man, but the victim did not want King to be punished, so the case was dropped.

King slapped the man in the face after he refused to serve a drink in a club. The victim was also a customer there, according to the court ruling.

Travelers watch an electronic departure board sign in Incheon Airport on July 27. (Yonhap)

Under USFK regulations, immediate steps shall be taken to remove a service member from South Korea and to preclude assignment to the country after judicial proceedings against him or her for a serious violation of the law are complete.

But as King completed his judicial proceedings, there was no way for the South Korean government body in charge of immigration to learn that King should be subject to an escort watch, or to exercise its authority to do so. The government's status of forces agreement with the USFK has minimized the procedure for affiliated members to arrive at or depart from South Korea, while the USFK's own welcome desk takes charge on their way from or to a US military base in South Korea.

"Korea's immigration authorities will unlikely be aware of the information about (those with SOFA status) who are supposed to be under the watch of an escort, unless we get notification from the USFK of the person's departure," a spokesperson from the Ministry of Justice said.

The Justice Ministry oversees matters of immigration concerning the jurisdiction of South Korea, while the matter of arrival and departure of people with SOFA status is largely out of their hands.

The ministry has the authority to suspend the departure of foreigners in case a criminal court trial is pending or if they have not completed imprisonment or payment of a fine, among other reasons as prescribed in the Immigration Act. Otherwise, the Justice Ministry's role in controlling immigration is limited, unless the ministry works with the USFK, it added.

The same is true for Incheon International Airport Corp., the state-run company in charge of operating the airport and handling security checks for passengers who are about to board an airplane. Its spokesperson said its responsibilities in terms of departure management are limited to checking whether a traveler holds a valid flight ticket and a valid passport, and whether the traveler possesses prohibited goods as he or she passes through the security gate.

This photo shows travelers waiting to get a security check to enter the duty-free zone and take a flight in Incheon Airport on July 28. (Yonhap)

Meanwhile, the Justice Ministry added that the government is not able to track the whereabouts of a foreigner who has aborted the departure procedure and to learn when he or she would return to depart from Korea.

"Whether to cancel immigration procedure (after entering the duty-free zone) and when to fly out is a matter of personal choice, so there is no specific procedure (from immigration authorities) to keep track of the whereabouts of those who canceled the immigration," the Justice Ministry spokesperson said.

In normal cases, those whose flight was grounded, who experienced a change of flight schedule, who suffered a sickness or lost belongings -- among other extraordinary circumstances -- may accompany a staff member of the airline company and request the cancellation of the immigration procedure, it added.

"If you heard about the death of someone close to you when you are at the duty-free zone, you may choose to go on to depart the country or to cancel the departure and attend the funeral," a source who wished to be anonymous said as an example.

The Justice Ministry did not comment on inquiries about any progress in joint monitoring of those with SOFA status.

"It is the USFK's responsibility to escort someone who needs to be escorted if the person belongs to USFK," another source said on condition of anonymity.

When asked whether USFK is discussing with Korea's immigration authorities over new ways to jointly monitor those whose judicial proceedings are complete but still needs an escort watch on their way back to the US, a USFK spokesperson said it is "a part of the investigation that is ongoing."

“Korean People's Army (of North Korea) has responded to the United Nations Command with regards to Private King. In order not to interfere with our efforts to get him home, we will not go into details at this time,” said Col. Isaac Taylor, director of public affairs at the United Nations Command.