The Senate Judiciary Committee has approved an assault weapons ban in a party -line vote that underscores how hard it will be for the measure to survive in the full Senate.
The proposal by California Democratic Sen. Dianne Feinstein was approved on a 10-8 vote Thursday by the Democratic-controlled committee.
An assault rifle was used by the man who killed 26 students and staff at Sandy Hook Elementary School in Newtown, Conn., in December.
Banning the weapons is key to President Barack Obama's plan to curb gun violence.
The measure is not expected to survive in the Senate.
Feinstein faces overwhelming GOP opposition and likely defections by up to six moderate Democrats facing re-election next year in Republican-leaning states in the South and West.
The senior senator from California sparred with Republican Senator Ted Cruz of Texas over protections offered in the Bill of Rights.
"Would she consider it constitutional for Congress to specify that the First Amendment shall apply only to the following books and shall not apply to the books that Congress has deemed outside of the protection of the Bill of Rights?" Cruz asked Feinstein.
Cruz opposes the weapons ban and is a defendant of the Second Amendment, which guarantees the right to bear arms. The First Amendment protects free speech.
"I've studied the Constitution myself," replied Feinstein. "I am reasonably well educated, and I thank you for the lecture."
Feinstein went on to explain that the bill exempts 2,271 weapons from the assault weapons ban.
"Isn't that enough for the people in the United States? Do they need a bazooka?" asked Feintsein.
She later conceed to Cruz that it would not be appropriate for Congress to specify which books could be exempted from First Amendment protection, but that Congress is in the business of making laws.
She says it's up to the courts to interpret them.