President Bush, joined by "America's Most Wanted" host John Walsh, signed a new law Thursday that requires convicted child molesters to be listed on a national Internet database and face a felony charge for failing to update their whereabouts.

"Our nation grieves with every family that's suffered the unbearable pain of a child whose been abducted or abused," Bush said in a bill-signing ceremony in the Rose Garden. "This law takes an important step forward in this country's efforts to protect those who cannot protect themselves."

The measure was named for Walsh's 6-year-old son, Adam, who was abducted exactly 25 years ago Thursday, and subsequently murdered.

It aims to help police find more than 100,000 sex offenders by creating the first national online listing available to the public and searchable by ZIP code. It also called for harsh federal punishment for sexually assaulting children, including the possibility of the death penalty when a victim is murdered.

"Today is truly a family day for us," Walsh's wife, Reve, told reporters outside the West Wing following the event. "Adam's presence is felt here with us today. This is all about children. It tells children in our country that they are precious and are cared about — even though they don't have any money, or vote or lobby — that we will take care of them."

Bush said the new law will help prevent child abuse by creating the national child abuse registry, and requiring investigators to do background checks on adoptive and foster parents before they are approved to take custody of a child. Giving child protective services professionals in all 50 states access to this information will improve their ability to investigate their child abuse cases, he said.

"These improvements will help prevent sex offenders from evading detection by moving from one state to the next," Bush said.

Child advocates have called the bill the most sweeping sex offender legislation to target pedophiles in years. It would:

—Establish a comprehensive federal DNA database of material collected from convicted molesters, and procedures for the routine DNA collection and comparison to the database when someone has been convicted of such an offense.

—Provide federal funding for states to track pedophiles using global positioning devices.

—Allow victims of child abuse to sue their molesters.

The law imposes a mandatory minimum sentence of 30 years for raping a child; a mandatory 10-year penalty for sex trafficking offenses involving children and for coercing child prostitution; and increases minimum sentences for molesters who travel between states.

Sen. John Kerry, D-Mass., said the measure the president signed into law closes loopholes in current child Internet pornography laws. The senator and co-sponsor, Sen. Johnny Isakson, R-Ga., pushed to include what they dubbed "Masha's Law" into the legislation Bush signed.

Now 13, Masha Allen was adopted from a Russian orphanage at age 5 by a man who sexually abused her. Her abuser was convicted, yet her images on the Internet are being downloaded around the world.

"It's an absolute outrage that the penalty for downloading songs illegally off the Internet was three times the penalty for downloading disgusting images of children," Kerry said. "We need to do everything we can to end the disgrace of child pornography. This is a start."

The new law dramatically increases penalties for anyone who downloads child pornography off the Internet, raising the civil penalties from $50,000 to $150,000. It will also change existing law to allow victims ages 18 or older to recover damages from those who downloaded images of them taken while they were children.