The Microsoft Root Certificate Program supports the distribution of root certificates, enabling customers to trust Windows products. As previously announced, the United States Federal PKI team formally requested the removal of the "Federal Common Policy" root certificate, also known as the "G1" root certificate, from the Microsoft Trusted Root Program.
On May 24, the "G1" root certificate is being removed by an out-of-band update. It's important that system administrators implement the "G2" root certificate, which replaces the "G1" certificate, before this date. Applications and operations which depend on the "G1" root certificate will fail after the retirement of the certificate on this date.
Removal of the U.S. Federal Common Policy CA certificate from the Microsoft trusted root - Windows Server
Discusses the removal of U.S. "G1" root certificate and provides solutions to avoid issues.