Join Date: Jan 2010
Location: Calgary, Alberta
Programs: Hyatt Diamond, Fairmont Platinum, Aeroplan Diamond, HHonors Gold, SPG Gold
Posts: 18,686
Typically seat jumpers will be removed if sitting in a seat that has been assigned..
I think its up to the FAs to police this.. if you have a concern, let the FA know.. but really beyond that, they are in charge of the cabin..