You can now use Amazon Route 53 Resolver endpoints for hybrid cloud configurations in the AWS GovCloud (US) Regions. These AWS Regions are isolated AWS Regions designed to allow U.S. government agencies and customers to move sensitive workloads into the cloud by addressing their specific regulatory and compliance requirements.

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/10/amazon-route-53-resolver-endpoints-for-hybrid-cloud-now-available-in-aws-govcloud-us-regions/