Another good one is that they are going to cross-ref loyalty cards with debit / credit card payments and anyone found to be stockpiling will be banned.
Just keep it as a rumour but put it out on social media and let it run.....
And another was to use the store CCTV and when anyone is seen to be overloading a siren will go off with an announcement, sort of Gazzumba, gazzumba "Lady in red jacket and black leggings buying up bog rolls, aisle three - red jacket and black leggings. Thank you."