This could get ugly. The real answer for me is I am not sure of the absolute legal, no loop holes, code compliant answer short of rewiring the circuit. I have heard of people pigtailing thhn to the wires and connecting them to the light. Honestly I just install the fixtures. It seems that all fixtures these days have this requirement and I would bet there are more installed "illegaly" than not. I believe this is more of a cover your ass from the manufacturers than any horrific safety hazard. Regardless of the wire type the fact is if it is not bright enough people will not hesitate to install the higest wattage bulb they can find. That to me would be far more of a hazard.
