ICAO Annex 14 (which deals primarily with SARPS for international airports) outlines requirements for rescue and firefighting that the airports shall have based on the fuselage lengths of the planes that visit said airports. Each category would define the equipment, amount of foam, discharge rate, etc.
Here the international airports comply with the users' requirements. It made me think of the other way around.
Suppose a pilot flies a tiny GA plane to a remote uncontrolled airport on a scenic tour. I don't expect that airport to have any means of rescue and firefighting apart from perhaps a call made to the local police.
But now suppose an air carrier decides to carry passengers to that airport.
Are there regulations that limit the airports an air carrier can visit based on rescue equipment? If not, how is the minimum level/category of rescue and firefighting guaranteed when not dealing with international airports?