The state of New York now requires a buyer to be 21 years old before purchasing a semi-automatic rifle such as an AR-15.
Previously, an 18-year-old could have purchased similar guns.
Democratic Governor Kathy Hochul Monday signed the measure, which was among 10 other gun-related laws.
"Today is the start, and it's not the end," Hochul said at a press conference in the Bronx. "Thoughts and prayers won't fix this, but taking strong action will. We will do that in the name of the lives that have been lost, for the parents who will no longer see their children stepping off the school bus."
The move comes against a wave of mass shootings, including the deaths of 10 African Americans at a Buffalo grocery store on May 14 and the May 24 mass shooting at an elementary school in Uvalde, Texas, that left 19 children and two teachers dead.
Other laws signed by Hochul would largely ban the sale of body armor vests and revise the state’s “red flag” law, which would allow authorities to seize guns from people deemed a threat to themselves or others.
One news report said the measures passed mainly along party lines and that Republicans were mostly opposed to the bills.
Some information in this report comes from The Associated Press and Reuters.