Datalist Group I rule function

I think your code looks good. Depending on what version you're running, you could use class instead of matchclass.

when CLIENT_ACCEPTED  {
    if {[class match [IP::client_addr] equals Pool_Test_Allowed_List]} {
        Uncomment the line below to turn on logging.
        log local0. "Valid client IP: [IP::client_addr] - forwarding traffic"
   } else {
        Comment the line below to turn off logging.
        log local0.  "Invalid client IP: [IP::client_addr] - discarding traffic"
        discard
    }
}