Why is it legal for some states to regulate the buying and carrying of guns?
Good question- without a really good answer. The 2nd amendment to the US Constitution provides that the "right to bear arms" "shall not be infringed". However, this issue has only partly been ruled on by the US Supreme Court. Thus both State and Federal laws that DO infringe on the right to bear arms have remained in force. The Court has ruled that a blanket prohibition against possession of firearms is NOT legal, but other laws (several thousand of them) remain in force.
It is legal in the United States to carry a Taser in most states. Exceptions are Conneticut (where you can keep one in your home but not carry it), Hawaii, Massachusetts, New Jersey, New York, North Carolina (again, legal on your property but not carrying), and Rhode Island, and the District of Columbia. Some states require a permit to carry, including Illinois, Iowa, Michigan, Mississippi, and Wisconsin.
In most states an 18-year-old would be considered a legal adult. The legal age of majority however does not change the specified legal age of the state pertaining to other issues such as buying or consuming alcoholic beverages. In four states the legal age of majority is higher than 18-years; in Alabama and Nebraska the legal age is 19, in Mississippi and Pennsylvania it is 21.