Law handed down orally. Enforced by elders and peer pressure.
Circuit overseer told the story in one of those 'OBEY or else' talks about an elder from a foreign country who came to the US. He had a beard, the local elders thought it looked fine, no action taken. Along comes the CO who chided the elders for allowing it. Made them tell the bearded elder to lose it or be removed. Why? As the CO said in the talk, 'It's just not done. What is more important? Following rules or demanding personal rights?' The CO was happy to report that the bearded elder shaved his beard and fell in line with rest of the sheep.
I asked an elder about it one time. He gave me the 'don't want to give the org a bad rep' excuse. He then went on to explain how large corporations have grooming rules for employees. They don't want exposed tattoos, body piercings, facial hair, etc etc. All about the reputation of the corporation. That was the day I finally realized that I wasn't a member of the one true religion, but an unpaid employee for a publishing company.