Joint Nuclear Weapons Control?

Question

As stated in a previous question, the main political entity of my world, the United Commonwealth, is protected by a combined Army and Navy, made up of personnel from all nations, and funded by all nations.

However, one topic I am still working out is the control of nuclear weaponry. While the Army/Navy split of responsibility is fairly straightforward, what I haven't fully figured out is how the authority to use these strategic nuclear weapons would be shared. To make it slightly easier, the United Commonwealth operates under a 'No First Strike' policy, so no one will be starting any nuclear wars, at least within the U.C.

However, this still leaves the use of nuclear weapons in a defensive way, as retaliation and deterrence.

Current Solutions

I've worked out 2 possible solutions to this issue.

1. Have control of nuclear weapons be surrendered to groups of national governments on each individual planet. Since there are 12 planets, that would mean 12 separate groups, each with control over nuclear weapons use and deterrence, and whether or not to even have them on their planet.

2. Have control of nuclear weapons be surrendered to the United Commonwealth itself, which is to say, have it be shared in some way among the U.C. Parliament, made up of elected representatives from member states, the Commission of the U.C., which carries out policy, and the Council of Nations, which is comprised of member nation's Heads of State/Government.

Which of these two would be the 'superior' method, or would be more likely to exist, or are both of these impossible. If so, what would be another way of accomplishing Joint Control, preferably without anyone just saying that the whole idea is impossible, or that the the UC should just split itself up.

Background Information:

1. Nuclear weapons are primarily missile based, on both ground launchers and silos, and nuclear submarines
2. Nuclear weapons technology itself is more or less open source, but the qeapons themselves are entirely reserved for world power nations, such as the U.C. and it's main rival, the People's Union of Bothnia.
3. The U.C is a made up entirely of democratic, liberal countries, while the P.U.B is a USSR style autocracy.
4. The discovery of nuclear weapons tech. was a result of joint U.C. research, which is why its control has to be shared.

Answer 1

What makes nukes so special?

On Earth, they are weapons of mass destruction. That's a very interesting term. As far as I know, US domestic criminal law defines even a hand grenade as a weapon of mass destruction. (§2332a references §921 which is pretty much anything explosive.) That's because it can be more lethal than the constitutionally protected handguns, rifles, and shotguns. But what is the difference between releasing an bomber raid with incideniaries and one with a nuke?

Well, one difference is that radioactive fallout lasts a long time, and kills even people who survived the initial attack. There are and were attempts to make war "clean" in some way -- banning dumdum bullets but allowing full metal jackets. Another is that Hiroshima and Nagasaki were small nuclear weapons, compared to the ICBM which came later.

But your setting has multiple planets. The weapons release on one of them doesn't necessarily affect all of them. And I guess there is spaceflight, too. How do people feel about nuclear weapons in ship-to-ship combat?

What that suggests to me is that the distinction between WMD-in-the-military-sense and non-WMD should weaken. (And also that no first use goes out of the airlock.)

Any official or officer who is allowed to release a thousand 2,000-lb. bombs should also be allowed to release nukes in your setting. Or the other way around, nobody who isn't allowed to release nukes should be allowed to release a thousand 2,000-lb. bombs. Or even a dozen.

If there is instant FTL communication, that sounds fine. If not, you're back to warfare in the 18th or early 19th century mode, where the last battle might well be fought weeks or months after the end of the war, simply because fleet commanders at distant stations know no better.

Answer 2

Devolved to Planetary Governments

The use of nukes would be controlled by whatever governmental bodies exist on the planet. Beyond that and a demand that they all obey No-First-Strike policy the UC would likely stay out of it. I think there are fewreasons for this:

1: The obvious is that nukes effect the planet. To the UC a planetary nuclear exchange isn't likely to be much different than a planetary kinetic impactor exchange, or even a conventional war that managed to drop the same amount of destructive energy on the planet. But for the folks on the rock, the long-term nuclear effects are going to matter a lot more.

2: If the UC doesn't have instant communication, the central government isn't in a position to order a second strike in anything approaching a timely manner. A Planetary Governor in a Commonwealth setting, or even Great Powers on a planet with disunited rule, is not going to allow an "off-world" general/UC apparatchik to decide when X% of the planet is going to become uninhabited due to second strike. They'll (rightly) want to reserve that power to the polities that actually have to deal with the literal fallout.

3: Every planet is different. The launch decision for a single-world-government planet, or a planet with only a pair of friendly superpowers, is wildly different than a planet with 30 near-peers that go to war every couple decades. Or one with 30 near-peers that just mistrust the hell out of each other. Each planet would need different rules for who calls the launch. Heck, a sufficiently distrustful/fragmented planet might prefer an off-worlder hold the keys to the nukes! Others might prefer massive devolution in control in the hopes that MAD stops the cycle of planetary warfare.