The owning isn't legally an issue in the vast majority of (American) places. Behavior with it, though, is - often municipalities require 'weapons' to transported in a locked container (often, the trunk of your car would count) and permit law enforcement agents to arrest anyone 'brandishing' a weapon. Note that the definition of 'brandishing' is at the discretion of the arresting officer, and if you can convince them you're harmless, you won't get another chance until you're in front of a judge.