WCF security mode="None" and still get client ssl

I have a WCF service that must be consumed by multiple client types (non .net).  These clients will be passing SSL certificates for verification of who they are.  In order for this to work with SOAPUI, it appears I need to set the security mode to none however when I do this, the  ServiceSecurityContext.Current.PrimaryIdentity is null. 
 
How can I get the client certificate when the security mode is set to none?
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