O'Rourke has become a champion for mandatory buybacks of assault weapons, such as AR-15s, that have been used in many recent mass shootings.
Still reeling from the mass shootings in Odessa and El Paso, the former Texas Representative told the Democratic debate crowd he would go beyond optional buybacks.
Thursday's decision looms large over both gun-rights supporters and gun violence prevention advocates, who are both keeping watch on Capitol Hill as Congress reconvenes and considers new federal gun control legislation.
"I don't know why it's taken 251 mass shootings now this year for people to start waking up," Christina Huelsman said.
In a New York Times op-ed, the presidential candidate for 2020 said: "We have to get these weapons of war off the streets."
If Congress won't work with her, Senator Harris plans to go it alone on an assault weapons ban should she ascend to the White House next fall.
"I want to get rid of that fear," said Representative Eric Swalwell, who launched his campaign for the Democratic presidential nomination last week.
AR-15s and large-capacity magazines are beyond the scope of the Second Amendment and may be banned, the court ruled.
Republican Kelli Stargel opposed a ban on assault weapons.
The motion comes less than a week after a gunman killed 17 people at a Florida high school.
The court found that military-style assault weapons and large-capacity magazines are not protected under the Second Amendment's right to bear arms.
Cluster bombs, chemical weapons and other banned weapons are now commonplace.
The Senate rejected four gun proposals in the wake of the Orlando massacre. Now what?
Top court may decide this week whether to hear challenges to laws in Connecticut and New York that ban semiautomatic weapons.
A group challenged an ordinance in Highland Park, Illinois, that bans assault weapons and large-capacity magazines.
There is an easy solution to America's arguments about gun control, but the childish extremists on both sides need to leave the room.