Elastic Load Balancing now supports TLS termination on Network Load Balancers in AWS GovCloud (US). With this new feature, you can offload the decryption/encryption of TLS traffic from your application servers to the Network Load Balancer, helping you to optimize the performance of your backend servers while keeping your workloads secure. Additionally, Network Load Balancers preserve the source IP of the clients to the back-end applications, while terminating TLS on the load balancer.

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/11/network-load-balancer-tls-termination-support-is-now-available-in-aws-govcloud-us/