In the airline world, we are allowed to refuel with pax onboard, and for this matter, even with patients, however, various rules need to be applied.
Seat belt sign off, and extra door is armed and manned by a cabin crew, the door must free of obstacles etc....A few things come into play, even sometimes you need to a have a fire truck near by.
Considering that at times that it can take 35 minutes to refuel 100 tons, and longer for more, these also cause problems for terminals and turn arounds, so it is a calculated risk, entirely up to the Captain.
These rules are governed by airlines, airport authorities, etc...most limiting of course applicable.