Both squadmates should have remembered the resignations put in by Dutch and Gretchen when they left the armed serves. Granted, that was when they were still just ODSTs and not genetically modified supermen with the most advanced, and expensive, armour technology available.
Come to think of it, I’m not sure if we’ve ever heard of any proper Spartans peacefully retiring into civilian life. Maria-062 went on to begin a family but she was still counted as a member of the reserves and was field testing MJOLNIR armour as late as 2552. I think the material that best analyses the idea of a full-fledged Spartan leaving military service comes in Mortal Dictata.
From Mortal Dictata:
Osman glanced at Naomi. “But the root of this is the UNSC taking your daughter and using her like a weapon. No choice. No consultation. Does she want to be swapped?” She held up a conceding hand. “I’m not lecturing you on morality. That would be disgraceful. I just don’t want to compound the original crime.”
“Is she free to leave the Navy?”
“Yes, she can put in her PVR request and ask for discharge like anyone else. Nobody owns her and nobody can stop her.”
“Really? Just like spies, huh? They can never leave. There’s always someone waiting to tap them on the shoulder to do one more job. Do any Spartans manage to retire?”
“I won’t lie to you. Only one Spartan’s ever retired, and that was another one like me who didn’t go through the full augmentation process, but most ended up MIA or KIA anyway.”
“Do you mind my asking if you meant what you said to Staffan, ma’am?”
She looked off to one side for a second. “I think I did. The question is whether he did.”
“And if Naomi wants to leave the service?”
“Then I have to ask myself if I believe what I say I do, or if I’m like all the others and I opt to solve it the ONI way. But a retired Spartan isn’t any more of a security risk than anyone else leaving special forces. Actually, much less.”
Those are quotes pertaining to the idea of Naomi-010 retiring and potentially returning to her family who happen to be insurrectionist operatives on Venezia. You have Osman’s personal sentiments and empathy for the injustices perpetrated against the families who lost young ones to the Spartan program. I think in her ideal scenario she would prefer to have everything get revealed to the public and for Spartans to be allowed to move on if they so wish. However, notice the final quote and how she establishes this conflict of operational procedures – there’s her own beliefs and then there’s what she refers to as the “ONI way”. What does that imply? Is ONI keen on allowing its treasured military assets, the Spartans, to freely walk away and do as they please? Well you wouldn’t have this differentiation into categories if Osman felt confident that allowing the Spartans the freedom to choose matched up with ONI’s modus operandi.
I think Mickey’s speculation of ONI not allowing him to walk away does hold some merit… that is after he became a Spartan. If he had chosen to hang up his helmet and rifle prior to the request then I think he wouldn’t have had any issues. It’s following the augmentation procedures and all the investment put into him that this becomes questionable.
Both Mickey and Buck had a point during that conversation. Mickey’s fault is not going through with his resignation before commiting himself to the UNSC via promotion to Spartan. Buck’s issue lies in him not appreciating the unscrupulous depths ONI will sink to in order to achieve their goals. The man should know considering his experiences with Dare.