It's about time to finally grok that all world's military is only there to wage wars at the whim of the 0.001% under the guise of being defence-only, and that constitutions worth less than toilet paper these days.
Kill the royal couples, no problem. There is an argument to be made that those that start wars should be sentenced to death for doing so. Particularly frivolous ones of aggression.
If the civilian populous has access to arms and armories they can make it a worthless proposition to invade them. Its not like the world is entirely composed of large countries with strong militaries already. An insurgency can last decades under fire from a superior force, an organized military won't. So if you can't match the organized military might of potential enemies, its probably mostly a waste to try.