Just imagine if the your ability to exercise your first amendment varied by where you happen to be standing. If you were standing in a State with Strict language control, it would be very different than standing in a State with minimal language control. Now add local ordinances that may vary from State laws. You would find that the ability to exercise your first amendment would be very problematic even for a law abiding citizen. But that is exactly what has been done with the 2nd Amendment. What is entirely legal in one area, could land you in jail in other areas. This nonsense has to end. If you can legally carry in your home state, you need to be able to legally carry wherever you are in the USA.
John Lott, jr (PhD in economics) wrote the book “More Guns, Less Crime.” The book examines city, county and state level data from the entire United States and measures the impact of 13 different types of gun control laws on crime rates.