In November 2009, President Obama traveled to the U.S. Army base at Fort Hood, Texas, to speak at a memorial service for 13 service members shot and killed during a rampage that wounded 29 others.

The president also spoke at a memorial service in January 2011 after a shooting spree outside a supermarket near Tucson, Ariz., that left six people dead and 13 injured, including then-U.S. Rep. Gabby Giffords.

Last July he visited Aurora, Colo., to console families, friends and colleagues after 12 people were shot to death and 58 were injured in a movie theater massacre.

On Sunday, when Mr. Obama met with and spoke to mourners in Newtown at an interfaith service for the 20 first-graders and six adults gunned down two days earlier at Sandy Hook Elementary School, he finally acknowledged what should have been addressed years ago: This nation can no longer tolerate such horrific, wanton gun carnage.

"Can we say that we're truly doing enough to give all the children of this country the chance they deserve to live out their lives in happiness and with purpose?" the president asked, as many in the audience at Newtown High School wept.

"If we're honest with ourselves, the answer is no," he said. "And we will have to change. What choice do we have? Are we really prepared to say that we're powerless in the face of such carnage, that the politics are too hard?"

President Obama pledged to lead a national effort to help bring about change, and without going into specifics his target was clear: gun control.

Because of the cowardice of lawmakers when threatened by the biggest bully in the political playground, the National Rifle Association, the president and Congress almost never take up gun legislation.

But the unspeakable horror at Newtown has given them cover, and the drumbeat for meaningful reform at last is resonating loudly.

It now seems certain that Congress at the very least will consider the most obvious legislation, a federal ban of so-called assault weapons. Sen. Dianne Feinstein (D-Calif.) said Sunday she would introduce an act to ban these weapons at the start of the next Congress in January, and a number of other lawmakers have pledged to support it.

This is a good sign, but any such law must be more effective than the loophole-ridden legislation passed in 1994, which Congress cravenly allowed to expire in 2004.

We also support the creation of a federal panel that would examine this nation's culture of violence that many believe has contributed to the mayhem.

As for any proposed gun legislation, part of the problem has been defining what constitutes an assault weapon.

As The Washington Post explained this week, there are fully automatic weapons, which fire continuously when the trigger is held down. Those have been strictly regulated since 1934. Then there are semiautomatic weapons that reload automatically but fire only once each time the trigger is depressed. Semiautomatic pistols and rifles come in all shapes and sizes and are extremely common in the United States.

This newspaper believes any such law must first acknowledge that weapons such as the AR-15 semiautomatic rifle Adam Lanza used Friday to rapidly fire multiple, high-velocity rounds inside the elementary school has only one function: to kill a lot of people quickly.

It is not designed to be used for hunting, to ward off burglars, for self-protection or any other purpose the Second Amendment fanatics hide behind when they speciously invoke their Constitutional right to bear arms.

Back in the 1700s the framers of that hallowed document never could imagine such a hideously effective killing machine.

Ordinary civilians aren't allowed to own shoulder-fired missiles and similar military weapons, so there's ample precedent for federal regulation of firearms.

The 1994 ban prohibited ownership of 18 specific firearms, as well as certain military-type features on guns. It also restricted the capacity of magazines to no more than 10 bullets.

But that legislation inserted a grandfather clause that exempted all assault weapons and magazines made before 1994. Therefore, it was legal to buy or sell an estimated 1.5 million assault weapons and more than 24 million high-capacity magazines already manufactured.

Congress must not make the same mistake.

We must hold President Obama to his word, and not allow him or Congress to dodge the bullet this time around.