You really should read the analyses people are posting about that. I don't know of any credible people saying it's flat-out always illegal to remove someone aft

You really should read the analyses people are posting about that. I don't know of any credible people saying it's flat-out always illegal to remove someone after allowing them onboard, but I do know of credible people saying the legally and contractually permitted reasons for it are few in number and the reason given in this situation (to make room for deadheading crew) is not one of those permitted reasons.