They have now returned to North Korea, where President Trump and the U.S. national-security establishment are trying to kill them.
That's what U.S. sanctions against North Korea are designed to do — to kill the North Korean citizenry through starvation or illness as a way to get regime change, one that will oust the communist regime headed by Kim Jong-un and replace it with a pro-U.S. dictatorship.
As an increasing number of people die in North Korea from the economic damage wreaked by the sanctions, several possible outcomes could ensue:
First, the North Korean regime could decide to save its citizenry by asking the U.S. to lift the sanctions in return for dismantling its nuclear weapon program. That is not likely to happen. No regime likes being pressured by a foreign regime into doing anything.