Setting VLAN based on Certificate Issuer

I thought this was a FAQ but apparently it isn't. I have an 1.1.7 FreeRADIUS server up and running with EAP/TLS. Now, I would like to put clients into different VLANs based on who signed their certificate. Is there a way to set the Tunnel-Private-Group-Id attribute based on the certificate issuer? Is the Rlm_eap module able to export any information on the certificate chain? Switching to 2.1.1 wouldn't be a problem for me I suppose. Thanks for any help.