SEATTLE -- Starting Tuesday, no one under the age of 21 in Washington state will be allowed to purchase a "semi-automatic assault rifle."
The new law goes into effect after Washington voters passed Initiative 1639 in the November general election.
Initiative 1639 was a sweeping measure that sought to curb gun violence by toughening background checks for people buying assault rifles, increasing the age limit to buy those firearms and requiring the safe storage of all guns.
Only the age-limit portion of the measure goes into effect on Jan. 1, 2019. The rest of the initiative becomes law on July 1, 2019.
Supporters of the measure say it will prevent gun violence by setting limits on the sale of the type of rifles most commonly used in mass shootings.
But opponents say it violates the constitutional rights of young adults. They've file a federal lawsuit to block the measure.