Gun control
The 2nd Amendment to the United States Constitution Amendment says, "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."  This is taken to mean, every American citizen has the right to "keep and bear arms".  Originally, it was thought that the federal government could not ban guns, but states and cities could.  However, in 2010, the Supreme Court said that states and cities could not ban handguns.  Although banning all guns is not allowed anymore, states and cities can still stop the sale and use of certain kinds of guns, such as automatic rifles that fire many bullets very quickly.  They can also say that certain people, such as criminals, cannot own guns.