Unless you are entering buildings with metal detectors or subject to search the key word is DISCRETE
Absolutely. If you do nothing to draw attention to yourself, the fact that you are carrying an item that is not allowed in a particular situation or location will never be known by anyone else but yourself. And if by chance you needed to use that item to save you or someone else, there is an old adage, "Better to be tried by 12 than carried by 6".