The crew commander, Sukjin Han, an assistant professor of economics at the University of Texas at Austin from South Korea, told me he signed off on most of the important decisions during the mission, but that he made sure to “hear the thoughts and opinions of all crew members beforehand and reflect them in the decisions.” In the tense moments after the accident, Han went with the majority.
This reminds of the "Das Experiment" movie, where students get to play prison guards and inmates and things quickly escalate. Certainly the mission commander has no legal right in any sense of the word to withhold medical treatment from a participant. It is not "his decision." The situation may or may not have been different if this were a military operation, but certainly participating in a simulation does not raise your authority and decision-making rights to such a level. It is only the decision of the injured and if they were incapacitated, it is the obligation of everyone else to make the call.