Use the ICISite interface SetCheckClientCert method to enable or disable the requirement of certificates on implicit SSL sites. If you must restart the server for the change to take effect the SetCheckClientCert method returns a value of TRUE.
Signature:
HRESULT SetCheckClientCert(
[in] VARIANT_BOOL newVal,
[out, retval] VARIANT_BOOL *pNeedRestart);
Refer to Site Certificates and Keys Parameters for an illustration of how this and other ICISite methods can be accessed in the Administrator interface.