By talking about illegal substance use within 'earshot' of the cameras you put the shop at risk.

If the shop is robbed or broken into, which happens frequently at shops selling drug paraphenalia, the tapes will be reviewed for information on the break-in. If, during that review, it becomes clear that the shop is allowing talk of illegal drug use on its premises, now the shop is in trouble, even worse than taking a loss due to a robbery.

If you like the shop and respect its staff, do them a favor and make sure you're only talking about tobacco, 'legal herbal highs', etc, and not weed.