The last time the U.S. government passed a gun control bill was 25 years ago.
The bill: Federal Assault Weapons Ban
Year passed: 1994
Provisions: It banned the manufacture, transfer or possession of "semiautomatic assault weapons," defined as military-style assault weapons, including the AR-15.
Effect: A recent study found mass shooting fatalities were 70% less likely to occur while the ban was in place.
Expiration: The ban expired in 2004, as was stipulated in the legislation.
Reintroduction: Several attempts were made to re-enact the ban, including after the 2013 Sandy Hook Elementary School shooting, which killed 26 people, including 20 children. It was never was renewed.