I have a customer who is trying to sell a home that has a 200A service panel being supplied by 2 AWG aluminum conductors. A home inspector for the buyers discovered this and of course wants it rectified. I told him we would need 4/0 aluminum and gave him the cost to do the job. He asked me if I could just replace the 200A main breaker with a 100A breaker. The house is about 1200 sq ft with no basement and the load could be served by a 100A service. I can not find anything in article 230 that would prohibit this. Just replacing the breaker would be a lot less expensive for him as the path from the meter to the main breaker box will require some work. I don't see the 100A breaker as a code violation but thought I would ask here to get some opinions.