Badges. While Government badges are not considered a copyright issue, it can be a forgery issue. To avoid that altogether, do not use the real badge of any government agency. In fact, pass all badges, logos, signs, banners and anything else through clearance just to steer clear of any potential problems. This goes for product placement as well. Everything has to go through clearance and everything has to be returned because the show will get charged for missing items.
While we are on the subject of props, prop houses are actually notorious for not having the rights to items they are renting out to you. To circumvent problems here, you must see any and all paperwork from a prop house and you need a signed agreement from them before you can use any props. Prop houses can be tricky because they often want you to sign an invoice which will state additional conditions in small letters that may get you into serious trouble. These are invoices that you should pass on to clearance before letting the ink dry.