Can a CSM prohibit a SGT from establishing joint domicile?

This is just a guess.... It seems his orders and his base type are in conflict with each other. It seems the CSM is trying to follow the base guidelines for that base, while the MOS branch awarded something that doesn't work for that base. The problem appears to be with the unit assignment not being compatible with the orders, (either in base type - no "off post" privileges, or its distance away from yours - 50 mile radius is a long distance for 100% alerts to handle) in which case a unit reassignment for him is appropriate to match his orders. A CSM operates in accordance with what orders he or she is given, whether that be base commander's policy, or threat-con level, or deploy-ability status of the unit in question (One of these seems likeliest). A CSM can use some discretion whenever a specific skilled task is highly needed, or when a soldier has been in trouble (It doesn't sound like these are the problem here). Privileges (like leaving post) can be revoked for many reasons.
If reassignment is best, and that base/unit won't do it, you gotta go higher - maybe 8th Army HQ. When I was there, I was offered a similar assignment, where my wife and kids would live off-post and I could visit every other weekend. The orders simply allowed for moving costs and for her to live in country - it didn't give me visiting privileges. Those came from my unit. For the unit I was in, we were all locked down for rapid-deployment 12 days in a row with 2 off following that. The C-of-C wasn't going to deal with people off post trying to get on post every time the whistle blew. But I was in infantry and further north. The only way for me to get better privileges would have been to have been stationed further south at a "friendlier" base.
Another possibility is that the post he is at is not used to orders of this type, and may not know what to do with them. If he is in-processing still, he may be getting conflicting information. His actual First Sergeant or C.O. at his destination unit will be the ones to award "off post" privileges. Even in my unit, I knew several persons who the C.O. allowed to live "off post" as long as they kept their nose clean - no trouble with M.P.'s, no missing mandatory stuff, always made it to alert formation on time, etc.

Well I Agee with the others. Joint domicile is just that. Joint. I would also go to JAG and contest his commands orders.

When I was in back in the 80s there were, CSMs and Commanders, like that. I would talk too a Jag officer adout that.

The biggest issue I see here is that you and your husband are in separate branches of service. If that's the case, and your husband is AF, he is limited where he can go. Are both or one of you in a critical MOS? That would determine what the long answer would be, short answer see IG.

What was the outcome

50 miles in Korea is a lot different than 50 miles in the US. I think this is more complicated than a paragraph allows.

I can't believe that the people in the Army are still playing silly games. What sens does it make for a SGT in the US Army to stay in the barracks while Joint domicile? If I was in that situation, I would take it over his head, that's foolishness... What if the roles were reversed and it was the SGM's? I bet he wouldn't want to stay in the barracks!!!! Smh... Silliness...

Joint domicile is just that joint domicile. But depending on unit needs could be and exception.. Highly unlikely.

Sgt. The CSM can not over orders

This sounds like the unit leadership is not explaining what is going on. Communication is essentail in an effective unit.