Answer:
The right to own a handgun for self-defense is a fundamental liberty, thus the states cannot violate that right because of the due process clause of the 14th amendment.
Explanation:
On June 28, 2010, the Supreme Court ruled in the McDonald v Chicago case that the Second Amendment to the US Constitution (which guarantees "the right of the people to keep and bear arms") applies to both state and local governments, which means individual states could not violate that right.