Are you saying that the airlines have a legal responsibility to only allocate emergency exit seats to 'fit and able' people?
Yes, absolutely. The subjectivity arises as to how 'fit and able" is defined.
The list of unsuitable occupants is ssentially as follows (there are some minor airline/national variations).
- No Children
- No Obese
- No Disabled
- No Prisoners in Custody/Deportees
- No Infants
- No Elderly/Frail
Dealing with unsuitability? Requires tact and diplomacy and also a firm approach - but you do it. Sometimes I have swapped pax around for take-off and landing only, allowing them to occupy such seats in the cruise. Ultimately, if I get attitude and refusal, I inform the Captain and we go nowhere until it is resolved.
Done carefully, and with sensitivity and empathy, it is rarely a problem.