We have a “sealed containers for treats” rule enforced not by the BO, but by the naughty barn cats. They will rip through anything that isn’t large and hard enough that they can’t get their teeth through it. The first time I was amazed that the barn cats had ripped through a softer plastic tupperware container of horse cookies set on a shelf, BO shrugged and said “they do that.”
We (all two boarders and BO) do lots of baited PT with our horses, so it would be potentially challenging to not be allowed to keep treats in the barn at all.