We might consider the people involved, too: we learn that Kirk knows his regulations, and Spock no doubt knows them, too. But Pike's decision to rely on these two goons shows the ship was really short on experienced professionals from the get-go. Who else aboard the vessel would be in a position to quote regulations on Spock?
The Security team would be specifically trained in the subject of regulations, no doubt. But they hate Kirk's guts already; their current boss is about as raw a recruit as Kirk himself is; and whatever Spock did wrong, it probably was a minor formality rather than a major violation of basic rights and procedures.
McCoy might side with Kirk here. But the poor Doctor is unlikely to know the finer rules, and can't throw the book at Spock, not before going back to his cabin and reading it anyway.
Sulu could be pals with Kirk by now, but he's seeing two officers behave in a fashion unbecoming of an officer. He has to pick one, and Spock has more braid on his sleeve. Chekov... Is a kid.
Ultimately, I doubt there was much wrong formally with what Spock did - but stranding Kirk in a life-endangering way doesn't sound like something covered by the regs. What I suspect is that the ever-resourceful Kirk tried to tamper with the lockout of the lifepod while on his way down, and ended up misdirecting the pod to the icy wastes when it was supposed to soft-land next to Scotty's outpost initially...
Timo Saloniemi