The weird thing is that they already do have rules in place that ban some things.  You can't buy pet food with SNAP.  You can't buy restaurant food.  You can't buy vitamin pills.  You can't buy beer.  You can't buy paper plates.  All of these are food-related items that are already disallowed. It wouldn't be obviously harmful to add one more rule to a list like that.  There's already a system in place for this sort of banning.