He is saying that the result is the opposite of the intent of the law. Telling a single individual to stop using the bags shows it doesn't work. It's like yelling at a user during user testing that they should just click the obvious button.

Laws should have A/B testing before rolling out to everyone.

In that plastic bag bans with the same basic parameters were applied in a few cities before spreading, in this particular case there was a kid of A/B testing before they were applied to everyone (actually, still pretty fast from everyone).

The argument upthread is that one household's behavior wasn't what the law intended, which is hardly a compelling counterargument.