To be fair, given the feudal nature of 40k, pretty much the entire command crew is enveloped in the bubble of power, as I understand it. If someone shows up on your doorstep and says "I speak with the authority of Captain Killcrazy!" you better treat them as well as you would the captain himself.
The fact that one player is undeniably In Charge could cause disputes, but in most groups I've been in there's always one player with Strong Ideas who brings everyone else around to his way of thinking and is the party leader unofficially.