The definition of unlawful objects depends on where you are, and what the laws are. If you don't have a concealed weapon license, then even standing out in a field in the middle of nowhere, a gun in your pocket would still be unlawful. However, even if you do have a license, having that same gun close to a school or an airport would be unlawful. Right now, a tube of toothpaste in your carry-on bag is an unlawful object at an airport. Hopefully, toothpaste is pretty benign other places. In general, an unlawful object is anything that there are laws against... and in many places, the law supports whatever the local rules are.