From Wikipedia –
A breed is therefore not an objective or biologically verifiable classification, but instead a term of art amongst groups of breeders who share a consensus around what qualities make some members of a given species members of a nameable subset.[2]
Right. The breeders decide what a breed is. So, as I said, the APA and the breeders clubs must decide standards for each breed.
There will always be disagreement, though, because people have different opinions about each breed. But the easiest way is to go by the accepted standards.