The Missile Technology Control Regime is the international communities leading instrument for containing the proliferation of missile technologies. The situation regarding North Korea and Iran demonstrates its limitations, and those limitations ultimately derive from the fact that it is an entirely supply side approach to stemming the flow of missile technology.
That’s something you pick from a good article by Jeffrey Lewis at Foreign Affairs on North Korea, even though it isn’t explicitly stated.
We know that the intial basis of North Korea’s missile programme was the reverse engineering of Scud missiles, as related in the above linked article
The basis of North Korea’s missile force was a pair of Soviet-manufactured Scud-B missiles provided by Egypt in the late 1970s. Pyongyang is believed to have reverse engineered the Egyptian Scuds in order to create missiles of its own. Today, short-range Scud missiles form the bulk of North Korea’s arsenal and have been sold to countries around the world, including Egypt, Iran, Pakistan, Syria, Vietnam, Yemen, and the United Arab Emirates
A similar dynamic was at play with the Musudan
After the collapse of the Soviet Union in 1991, North Korea sought more advanced technologies for its missile program—technologies that would scale better than those in the Scud missiles supplied by Egypt. During the 1990s, reports emerged that engineers from Russia’s Makeyev Missile Design Bureau, which had designed the Soviet Union’s submarine-launched ballistic missiles (SLBMs), were helping Pyongyang to copy a Soviet-era SLBM called the SS-N-6.
These are the processes that brought about the MTCR.
The KN-12, it would seem (certainly the North Koreans say so) uses an indigenously designed engine, Lewis adopts the thesis that it was designed because North Korea couldn’t master submerged engine development. The SS-N-6 uses submerged engines. Even so, the SS-N-6 is an important part of the design history of “the March 18 engine.”
And of course, we have the two solid fuelled missiles the KN-11 and the KN-15. Some have argued that the KN-15 was developed with, either authorised or unauthorised, Chinese transfer of technologies however according to the CSIS database
Allegations have also been made that the KN-15 bears a great deal of similarity to the JL-1 and DF-21 missiles, and could have been produced from transferred Chinese technology. The allegations cite the KN-15’s rapid development time frame and its physical similarity. Physical characteristics, however, may not be a reliable indicator of the missile’s source, given the physical similarities of SLBMs in general, and solid-fueled missile more broadly. Moreover, the KN-15 appears to use a single engine, and employs grid fins for stability, whereas the JL-1 employs four engines, and no grid fins
The missile technology control regime has not prevented North Korea from making important, some of which are indigenous, advances in missile research and development. This means that on its own the MTCR cannot prevent a determined proliferator, even one as sanctioned and underdeveloped as North Korea, from advancing a ballistic missile programme designed to deliver nuclear weapons, and that includes both liquid and solid fuelled missiles as well as shorter range and longer range missiles.
The MTCR needs to be supplemented by demand side approaches, that is with diplomatic initiatives designed to address the underlying demand incentives driving missile proliferation. An important demand pull factor driving North Korean missile development was articulated in the Lewis article
There are obvious reasons for North Korea to seek the capability to strike the United States with a nuclear weapon. Washington is Pyongyang’s primary adversary and the one power in the world that threatens Kim Jong Un with the fate that befell Libyan dictator Muammar al-Qaddafi and Iraqi President Saddam Hussein: forcible regime change
Supply side approaches that ignore such demand pull effects, North Korea has shown us, are an inadequate means to meeting the challenge of missile proliferation. I suspect that supply side approaches are adopted, in part, to lower the cost of underlying strategic policies driving proliferation.
North Korea has shown that a state determined to raise the cost of such policies can do so despite the MTCR.