When adding an ACI (Access Control Instruction) to Red Hat Directory Server I receive an "Syntax Error"

Issue

• in our attempt to minimize insecure traffic with RHDS over port 389 (without SSL or TLS), I'm trying to construct an ACI which should do the following:
  • block all access to the directory server with a security strength factor lower than 56
  • exempt a specific list of users which are added in a group called cn=Insecure Access Users.
• So far, I have come up with the following ACI to place on the root suffix:

(targetattr = "*") (version 3.0;acl "No insecure access";deny (all)(groupdn != "ldap:///cn=Insecure Access Users,ou=Groups,dc=example,dc=com" and ssf<"56");)

• However, trying to add this aci gives a syntax error. I'm not sure why because I feel that this syntax should do the trick.