You have to change `access_decisions_manager` strategy from `affirmative` to `unanimous` otherwise builtin `AuthenticatedVoter` will vote for an `ACCESS_GRANTED` so access will be granted even if the `BetaVoter` votes `ACCESS_DENIED`. 

Why ? because `affirmative` strategy grant access to user when ONLY one of the voters votes `ACCESS_GRANTED`. `unanimous` is the opposite it denies access if ONLY ONE of the voters votes `ACCESS_DENIED`.