If you saw one of your Joes doing this, how would you react?

This is like going to the bar with you company and the new private shows up wearing a army t-shirt, jeans, and combat boots.

I would remind him that he's not a child anymore. Then, I would post this picture all over the unit.

Whatever is done you shouldn't embarrass this soldier in a public forum, ie comment on his photo. Send him a message letting him know what he did wrong and leave it at that

Just tell him it's out of regs, and let it go. But common sense should have told him to wear his appropriate uni for a formal event. It's not deserving the death penalty.

If I was going to break regulations to go to a prom in uniform.. (Which I wouldn't), I would at least wear my blues?

If I knew he was planning on doing this prior to prom, I would instruct him not to. Upon seeing this then his six would be on fire a little bit. If he did not come to me prior and I found out after the fact, well.....what's done is done but he would still receive some words from me.

So, who is failing in this photo? It's certainly not the relatively newly enlisted kid in the photo, is it? So this kid is right out of highschool, as his sweetheart is still in...probably home on hometown recruiting, or something similar, but lets assume hes on leave or pass for the event. Did he tell or inform his leadership of the event beforehand and ask for guidance as to what to wear? No, of course not, because all of you guys here would do nothing more than clown him....including that comissioned officer down in the comments a bit, "dork", right? Maybe if soldiers were comfortable enough with their leadership to ask them simple advice about an area of their life that is important to them and not be worried that their leadership is going to "post this pic all over the unit", we wouldnt be having this discussion to begin with. Sire, dude is obviously wrong in his wardrobe choice, but who is really to blame? You guys routinely let me down in the shallowness of your observations. We might wear the stripes, but no way could it have been our fault, right?

Not knocking his character but totally out of regulation and to a prom. Tux it dude.

Well well. I agree paperwork is not in order, unless this is a repeat offense. And not knowing this is wrong is not an excuse, as everyone is instructed on it in basic. However, in my opinion, I would have a discussion with said individual, and make it crystal clear this is incorrect. I no longer know all the regs, however, he should be made aware of what it says, and that it was inappropriate and unbecoming and why, and since I'd assume he is a young man, chalk it up as a learning experience for him. At worst I would keep a notation on file, as to the discussion so if it does happen again that there is a record to fall back on, like we used to call letters of counseling.

Really, who gives a shit, we all did dumb shit as a Soldier. Nothing worse than a leader that forgets where he or she comes from. Use it as a teachable moment and explain the procedures. Oh, and the young man looks young, so if he is 18, and she is seventeen...well in a few years she will be 20 and he will be 21. Leave the poor kid alone, teach, train and mentor. That's what NCO's use to do. I guess getting a college degree is more important than taking care of Soldiers.