 Why doesn't the crew throw Moran out of the airlock?
The plans were thrashed out very painstakingly, in formal conference on the space-yacht Nadine , with Moran present and allowed to take part in the discussion. Moran observed these things from the control-room of the Nadine , then approaching the world on planetary drive. With clearance-papers in order, they could land unquestioned at any other space-port and take off again—provided the other space-port was one they had clearance for. Without rigid control of space-travel, any criminal anywhere could escape the consequences of any crime simply by buying a ticket to another world. Wherever the yacht landed, such a disparity between its documents and its crew would spark an investigation. Moran, at least, would be picked out as a fugitive from Coryus Three.
 They are not murderers.
 They are not murderers.  They do not want to be accused of aiding and abetting.  The crew will alert the authorities when they reach Loris. Moran will be brought to justice for his crime.  They are marooning him as punishment for murder.