Why is it that you don't have the same law for all your country?
Is it because of your size?
You have one president for your country why not one law for all?
Here we have one law for everyone.
We have what is called "States Rights", each state has the right to enact their own laws outside of the federal (national law). Open carry and concealed carry are states rights.
States rights is defined in the Tenth Amendment of the US Constitution.
Not all states have open carry or conceal carry laws, most do. Two states that ban both open and conceal carry are Illinois and New York.
Here in South Dakota we have both open and conceal carry permits. The cost is $10 and the permit is good for 4 years and you must get the permit from a local sheriff department. Once a resident passes a backgrund check, they are issued the permit.