Law not having CoC proves you can be a 3 billion tier without CoC so long as you are a DF merchant
However to be a 4 bil or 5 bil tier you need CoC from everything we have seen. All the pre skip yonko had CoC. WB had one of the strongest DFs and he still had CoC.
So at the very least we can say Akainu probably has CoC. Maybe Kuzan, as he was a fleet admiral candidate.