The bulk of airline certification authorities require a passenger to be seated in the exit row to operate the door immediately if required, along with all the specification of who can sit there or not. The Irish Aviation Authority very recently got into a compliance ruling on Ryanair, who were charging extra for the seats and letting them go empty if people didn't pay, and were giving the door opening additional briefing to passengers in seating rows BEHIND the exit rows to try and get compliance with their AOC.

I didn't hear what the final result of this was.