New York Gov. Katie Hockol has raised the age to buy a semi-automatic rifle from 18 to 21 as part of a move to tighten gun laws in the aftermath of the racist massacre at the Buffalo Mall.
Hockol passed a gun law reform package that was passed by the state Senate after 10 African Americans were shot last month.
The move comes in light of a series of shootings in the United States that have sparked renewed calls for tougher gun laws.
Payton Gendron, 18, is accused of killing shoppers on May 14 with an AR-15 he purchased legally.
Aside from the issue of age, buyers of semi-automatic rifles will now have to obtain a permit to own them, which means they will be subject to an investigation related to their history.
Democrat-run New York State largely enforces gun laws, which are among the strictest in the United States.
Hakol also agreed to expand state laws that allow courts to confiscate firearms from people they consider a danger to themselves and others.
Ten days after the Buffalo shooting, a teenager killed 19 children and two elementary school teachers in Yuvaldi, Texas.
US President Joe Biden has called for new laws to control gun ownership, including a ban on offensive weapons.
At the very least, he said, lawmakers should raise the age for buying assault weapons from 18 to 21.
But the issue of gun control is facing stiff resistance in the United States, much of it coming from Republicans and some rural Democrats.
According to the Archive of Gun Violence, more than 18,000 people died from gun violence in 2022, including 10,300 suicides.