In Washington, a semi-automatic assault rifle is defined by Initiative Measure 1639 as: "Any rifle which utilizes a portion of the energy of a firing cartridge to extract the fired cartridge case and chamber the next round, and which requires a separate pull of the trigger to fire each cartridge."

To purchase semi-automatic rifles as defined above, a person must be a resident of the state and minimum 21 years of age. This restriction does not include those rifles that are:

Antique firearms
Any firearm rendered permanently inoperable
Any firearm that is manually operated by a bolt, pump, lever, or slide action

Updated 12 June 2019