Let's return to the baseball analogy: So long as the pitcher releases the ball, anyone with a good video camera can tell how good his arm is, even without seeing the ball cross the plate. Similarly, North Korea will be able to tell, and show others, whether its missile works, even if the United States ultimately shoots down its payload.
The United States has backed itself into a no-win situation. For now, the United States would do best to stick to research and development on missile defense and save activation for genuinely dangerous situations. By wielding its missile defense now, it has increased the stakes for itself while leaving them unchanged for North Korea. Ironically, American military moves have made a diplomatic solution all the more urgent.