Market incentives (or disincentives, I suppose). The government doesn't regulate scuba diving, but no scuba outfit rents gear to someone without a PADI or NAUI or YMCA card.
Show me your 'MACO advanced aquarist card', or you can't buy that Heteractamumble latinithing!
Show me your 'MACO advanced aquarist card', or you can't buy that Heteractamumble latinithing!