Restores a certificate authority (CA) that is in the <code>DELETED</code> state. You can restore a CA during the period that you defined in the <b>PermanentDeletionTimeInDays</b> parameter of the <a href="https://docs.aws.amazon.com/privateca/latest/APIReference/API_DeleteCertificateAuthority.html">DeleteCertificateAuthority</a> action. Currently, you can specify 7 to 30 days. If you did not specify a <b>PermanentDeletionTimeInDays</b> value, by default you can restore the CA at any time in a 30 day period. You can check the time remaining in the restoration period of a private CA in the <code>DELETED</code> state by calling the <a href="https://docs.aws.amazon.com/privateca/latest/APIReference/API_DescribeCertificateAuthority.html">DescribeCertificateAuthority</a> or <a href="https://docs.aws.amazon.com/privateca/latest/APIReference/API_ListCertificateAuthorities.html">ListCertificateAuthorities</a> actions. The status of a restored CA is set to its pre-deletion status when the <b>RestoreCertificateAuthority</b> action returns. To change its status to <code>ACTIVE</code>, call the <a href="https://docs.aws.amazon.com/privateca/latest/APIReference/API_UpdateCertificateAuthority.html">UpdateCertificateAuthority</a> action. If the private CA was in the <code>PENDING_CERTIFICATE</code> state at deletion, you must use the <a href="https://docs.aws.amazon.com/privateca/latest/APIReference/API_ImportCertificateAuthorityCertificate.html">ImportCertificateAuthorityCertificate</a> action to import a certificate authority into the private CA before it can be activated. You cannot restore a CA after the restoration period has ended.