The U. S. Constitution states that "Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State." (Article IV, Section I, <a href="http://www.usconstitution.net/const.html">full text here</a>) This is one reason that your vehicle license plate and drivers license is accepted in all 50 states, no matter which state it was issued. However, a license to carry a concealed firearm is not treated the same way.