WASHINGTON -- The slaughter in Newtown, Conn., returns Democratic Sen. Dianne Feinstein to awfully familiar gun-control turf as she enters her third decade in the U.S. Senate.

Once again, the California lawmaker and her allies will be pushing for tougher firearms regulations, including a revived assault-weapon ban. Once again, the Capitol Hill debate will pit Second Amendment rights against ghosts from the latest calamity. If history repeats, the outcome will shape both public safety and some political futures.

“This is really the straw that breaks the camel’s back,” Feinstein said in an interview Monday. “I’m beside myself over this.”

A senior member of the Senate Judiciary Committee, re-elected in November to her fourth full term, the 79-year-old Feinstein is uniquely positioned to lead the coming gun-control debate. She authored the last federal assault weapon ban, a now-expired 1994 measure that cost some of her rural Democratic congressional colleagues their jobs.

Feinstein said she has been working for a year on the new bill she will introduce on the first day of the next Congress. She says it will ban the sale of more than 100 specified assault weapons, including the Bushmaster assault rifle used in Friday’s massacre, as well as ammo clips and drums containing more than 10 bullets. Similar to the 1994 law, she says the new proposal will exempt more than 900 specified firearms. Unlike the 1994 bill, though, the new version won’t be limited to 10 years.

“We have taken our old bill, and gone over it,” Feinstein said.

Feinstein added Monday that a House version of the bill will be authored by Rep. Ed Perlmutter, a Democrat whose Colorado district includes the city of Aurora, site of last summer’s movie theater mass murder. Other power players also will crowd the stage, including, in time, federal judges, who may hold the trump card.

“If the government is going to intrude on a fundamental right, they are going to have to have a compelling governmental interest and the law will have to be fitted to achieve those ends,” said San Jose, Calif.-based attorney Donald Kilmer, who represents the Calguns Foundation in lawsuits challenging gun laws, in an interview Monday.

Most recently, the 7th Circuit Court of Appeals on Dec. 11 struck down an Illinois law that prohibited most individuals other than hunters or law enforcement personnel from carrying weapons in public. The ruling relied, in part, on a 2008 Supreme Court decision striking down Washington, D.C.,’s strict handgun ban.

“The constitutional right of armed self-defense is broader than the right to have a gun in one’s home,” Judge Richard Posner wrote in striking down the Illinois law.

The 2008 Supreme Court ruling in the so-called Heller case that found the Constitution protects an individual’s right to own firearms will also shadow Feinstein’s new legislation. As of September 2012, the Law Center to Prevent Gun Violence had tallied more than 50 post-Heller civil lawsuits challenging state, local or federal firearms regulations.

“The issue is going to be whether the semiautomatic weapons are commonplace weapons that can be used in self-defense,” said Kilmer, whose current lawsuits include several involving California’s statewide assault weapon ban.