The bill would require anyone trying to obtain a weapon to pass the National Instant Criminal Background Check System (NICS). If the individual matches any of the prohibitive criteria, they may be denied from purchasing a firearm.
"We don't want to rob people of their constitutional right," Lautenberg told senators, "But to err on the side of protection is a chance we sometimes have to take."
Rep. Peter King, R-N.Y., who sponsored similar legislation in the House, urged senators to support the bipartisan bill.
"We cannot allow any more acts of violence on account of weapons legally falling into the hands of those who wish to commit acts of terror," King said. "We must do all that is possible to put tighter rules in place to assist law enforcement in their brave efforts to keep our cities and neighborhoods safe and secure. The war on terror must be fought from all directions if we're going to stay a step ahead of our enemies."
There is currently no law that prevents such people from obtaining a weapon. They can only be denied if they have a felony conviction or are illegal immigrants.
Terrorists could cause significant casualties if they successfully detonated explosives in the United States. But the alleged Times Square bomber, the alleged Christmas Day bomber and the men who plotted to release cyanide in the New York City subway could have something in common: failure.
Indeed, the only successful terror attacks perpetrated within the United States since 9/11 were with guns, a point Lieberman made in pushing for the legislation.
"The threat is real," he said. "Terrorists with high-powered automatic weapons could inflict heavy casualties in seconds."
There was spirited debate between Lieberman and Graham, normally allies on national security issues. Lieberman said Second Amendment rights, just like the First Amendment right to free speech, cannot be unlimited.
Graham said a person's rights as a citizen should be abridged if they are suspected of being a terrorist. He said authorities should be able to consult a secret FISA judge to keep a suspected terrorist such as Faisal Shahzad out of the legal system and without his or her Miranda rights.
"I don't think it's smart for us to say the homeland is not part of the battlefield," Graham said.
Bloomberg and New York Police Commissioner Raymond Kelly told senators that although the Times Square bombing attempt failed, terrorists are already plotting their next move,. The two lobbied Congress to ban people listed on the terror watch list from buying guns, and called it the "terror loophole."
"It is time to close the 'terror gap' in our gun laws," Bloomberg said. "At a time when the threat of terrorism is still very real, as we in New York City know all too well, it is imperative that Congress close this terror gap in our gun laws -- and close it quickly."
"This is not about the Second Amendment," he said.