Why didn't sanctions stop North Korea’s missile program?

Daniel Salisbury, DefenseNews (USA)
North Korea’s long-range missile program has made significant technological advances in the past few months. For most of the past 20 years, the international community has struggled to stop this kind of progress. North Korean leader Kim Jong Un’s plan to target four test missiles approximately 20 miles off the coast of the U.S. territory of Guam shows just how destabilizing this rapidly advancing ballistic missile program can be.