There is smuggling in North Korea between North Korea and South Korea and between North Korea and China. That's a huge market. When I was in North Korea and of course here now.... China's government cannot control the smuggling. Also, both Korean governments cannot control it. That's really underground.
Also, North Koreans are demanding information from the world outside North Korea. People require the information, especially merchants, who want to know the trends. They want to know about the outside world. They try to make money with that information, so they are growing right now. My answer is that the Chinese government and the North Korean government cannot control this smuggling.