Reports have come in stating the reason is he has not enrolled into VADA’s clean boxing program. Therefore, per WBC rules he’s been removed from their rankings.
This is nothing new and should not be a surprise to anyone involved. Back in April, the WBC revealed a list of fighters who were going to be dropped from their respective weight class rankings for the same reason.
Among the names was the legendary Manny Pacquiao, who has used VADA testing in the past (e.g. against Jessie Vargas). He has still not enrolled in the program and remains unranked.
Brook is coming off an impressive second-round stoppage victory over Siarhei Rabchanka in his hometown of Sheffield England. This coming off back-to-back losses against Errol Spence and Gennady Golovkin. Since losing those fights at welterweight and middleweight respectively, he decided to campaign at 154 pounds.
Fighters like Vanes Martirosyan and Amir Khan have been re-instated in the rankings by enrolling (or enrolled before being removed). Therefore, if Brook decides to enroll into the program, he will most likely be ranked again.