private boolean isNonArnOutpostRequest(Request<?> request) {
        AmazonWebServiceRequest originalRequest = request.getOriginalRequest();

        if (originalRequest instanceof CreateBucketRequest &&
            !StringUtils.isNullOrEmpty(((CreateBucketRequest) originalRequest).getOutpostId())) {
            return true;
        }

        return originalRequest instanceof ListRegionalBucketsRequest &&
               !StringUtils.isNullOrEmpty(((ListRegionalBucketsRequest) originalRequest).getOutpostId());
    }
It should redirect signer if the request is CreateBucketRequest or ListRegionalBucketsRequest with outpostId present
aws-java-sdk-s3control/src/main/java/com/amazonaws/services/s3control/internal/handlers/EndpointHandler.java