A lawless society is one without any rules or order. In some respects, the Old West era of the U.S. was a lawless time.
When you think of old-timey saloons and sheriffs and cowboys, you probably envision lawless bandits riding boldly into town — in other words, criminals accustomed to making their own rules, rather than following any established laws. A lawless city today is one that's in such chaos that order can't be kept, even by police officers. To be lawless is to be without law, which stems from the Old English lagu, "law or rule."