The most significant US gun control bill in nearly 30 years has been signed into law by President Joe Biden.
It imposes tougher checks on young buyers and encourages states to remove guns from people considered a threat.
Congress approved the legislation with bipartisan support this week, following a spate of mass shootings.
“While this bill doesn’t do everything I want, it does include actions I’ve long called for that are going to save lives,” Mr Biden admitted.
In May shootings at a supermarket in Buffalo, New York, and a primary school in Uvalde, Texas, left a total of 31 people dead.
As he signed the legislation on Saturday, Mr Biden said relatives of the victims expected the US government to do something. “Well today, we did,” he added.
The reforms include:
President Biden, as well as gun safety groups, had pushed for bigger reforms – including banning assault weapons, which were used in the Texas and Buffalo shootings – or at least an increase in the age at which they can be purchased.
The gunman in the Texas shooting is believed to have bought two semi-automatic rifles days after turning 18.
The new legislation is also significant because it is the first time in decades that the reforms have received support from both Democrats and Republicans.
Historically, efforts to strengthen US gun laws have been blocked by the Republican party.
The National Rifle Association (NRA) opposed the bill, arguing that it would not stop the violence.