The people who make the decision are not employed by the airline. They are employed by the airport, or by the government of the country in which the airport is located. It is not possible for one airline to decide it's ok for you to bring peanut butter and another to decide you can't, then try to instruct the security inspectors accordingly.
There are some matters that airlines decide for themselves, such as accepting sports equipment (surfboards) and the like as checked luggage. They also typically set the size and weight limits for your hand luggage. The actual rules for the contents ofThey can ban things on their own account, but they can't unban things that the luggage aresecurity agency has banned. That is simply out of the airline's hands. It's probably not the airport who decides, but the airport will have a copy of the rules, or will know who to refer you to next.
You will never see a standard for all airports, btw. Domestic flights in many small countries have literally no security inspection at all. I flew on planes where a passenger was carrying a machete wrapped up in newspaper. It wasn't even in a bag! That works for small places where domestic flights are unlikely terrorism targets.