@Override
    @JsonIgnore
    public boolean isProviderAllowed(final String provider, final RegisteredService registeredService) {
        if (getAllowedProviders() == null || getAllowedProviders().isEmpty()) {
            LOGGER.warn("Registered service [{}] does not define any authorized/supported delegated authentication providers. "
                        + "It is STRONGLY recommended that you authorize and assign providers to the service definition. "
                        + "While just a warning for now, this behavior will be enforced by CAS in future versions.",
                registeredService.getName());
            return this.permitUndefined;
        }
        return getAllowedProviders().contains(provider);
    }
This is {@link DefaultRegisteredServiceDelegatedAuthenticationPolicy}.

@author Misagh Moayyed
@since 5.2.0
core/cas-server-core-services-api/src/main/java/org/apereo/cas/services/DefaultRegisteredServiceDelegatedAuthenticationPolicy.java