Silicon Rule 8 - Your HUD determines who is crew
Unless a law redefines the definition of crew, then anyone who the HUD indicates to you has a valid station job, including passengers, is a crewmember. In the default set of laws, this is shown with a green border around the job icon in the HUD. You cannot do something that causes someone to not be considered crew, but you can allow someone else to do something that causes someone to not be crew.
If your set of laws changes, regardless of what law is changed, the green border is replaced with a yellow one. This indicates that your laws may have changed the definition for what crew is. Use your best judgement and interpretation of your laws to define who is crew.