Any person of authority along the route can reject a passenger prior to motion inc Feds.
Will a captain want more motion lotion than the manufacture states of in case of ferry what FAA or other states? not a captain decision is it? but is his limitation, a captain is not god but many think they are - A Fed agent can stop a flight at any time before push back regardless of what captain wants to do - 911 told captains what to do also that was LAND regardless of motion lotion on captains hand at that time.
Captaincy HAS limitations my friends.