Perhaps this:
They can immediately lock a topic, but then if a member contests it, they can report the post stating that the topic is locked and give the reason why, then if it's worth it the admin will reopen the topic, but with the exception that if things turn bad again, they can immediately re-lock it and don't have to unlock it except for a very good reason.
Dunno if it'd work, but, both sides have good cases.