Both US and Japan can't shoot it down once it reaches its planned altitude. If NK really is launching a satellite, it will be cruising at around 400km altitude, whereas Standard 3s will reach up to 200km altitude, 300km at the very most.
The only way it can be shot down without it malfunctioning, would be if they station DDGs very close to NK and shoot it down at early stages. This is unlikely, since it is equivalent as declaration of war and a slap in the face. No one dares to do something like this to a lunatic like NK, even the mighty Uncle Sam.