code: protected void verifyRegisteredService(final RequestContext requestContext, final RegisteredService registeredService) {
          if (registeredService == null || !registeredService.getAccessStrategy().isServiceAccessAllowed()) {
              LOGGER.debug("Service [{}] is not recognized/allowed by the CAS service registry", registeredService);
              if (registeredService != null) {
                  WebUtils.putUnauthorizedRedirectUrlIntoFlowScope(requestContext, registeredService.getAccessStrategy().getUnauthorizedRedirectUrl());
              }
              throw new UnauthorizedServiceException(UnauthorizedServiceException.CODE_UNAUTHZ_SERVICE, StringUtils.EMPTY);
          }
      }
docs: Verify registered service.
  
  @param requestContext    the request context
  @param registeredService the registered service