But sex offenders say they have rights, too, and argue it's wrong to lump those guilty of minor offenses with the worst offenders. Some are challenging the laws.
"People think that imposing these draconian retroactive laws are a way to keep their children safe," said Margaret McLetchie, an American Civil Liberties Union of Nevada lawyer.
McLetchie and Robert Langford, who represent 27 unnamed plaintiffs in a federal civil rights lawsuit, want to block two sex-offender laws from taking effect in Nevada.
The laws, which they say are unconstitutional, were tailored to meet standards under the Adam Walsh Child Protection and Safety Act, which President Bush signed in 2006.
Nevada was among the first to pass the laws that would allow the state to post on the Internet the names, photos, home and work addresses and vehicle descriptions of offenders who've served probation or prison sentences on convictions as far back as 1956.
McLetchie said the measures mix serious sex offenders with people convicted of misdemeanors such as public nudity and could subject them to violence from neighbors who see their names and photos.
"These laws don't provide public safety, they only demonize a particular group," she said.
But Binu Palal, the deputy state attorney general arguing the case for Nevada, said the law is constitutional and U.S. Supreme Court rulings from 2002 limit sex offenders' ability to block the release information about their crimes.
"The system is based on the fact of conviction," Palal said. "Informing the public of a true fact is not considered punishment."
U.S. District Court Judge James Mahan is scheduled to hear arguments Sept. 10 in the Nevada lawsuit. He is being asked to make permanent a temporary ban he imposed that stopped the law from taking effect July 1.
Mahan has expressed concerns that if Nevada posted its list of 4,941 people convicted of sex crimes since 1956, there would be no way to restore their privacy if the law was later found to be flawed.
Once posted, the judge said, "the cat's out of the bag."
His ruling is expected to be watched closely in states that have adopted or are considering provisions of the Adam Walsh Act, named for a 6-year-old Florida boy abducted and killed in 1981. He was the son of John Walsh, star of television's "America's Most Wanted."
Implementation has been challenged in some states, including Florida and Ohio.
"We've objected since it was first introduced in the Legislature," said Amy Borror, spokeswoman for the Ohio public defender's office in Columbus. "We believe it's unconstitutional when it's applied retroactively. Even going forward, it's bad policy."
Borror noted similarities between the Ohio and Nevada laws, and said officials in Ohio were watching the Nevada case with interest.
The Ohio registry went into effect Jan. 1 despite objections that it punished offenders twice, broke plea deals and represented a violation of states' rights by Congress. Furthermore, by creating the registry, the state Legislature usurped powers reserved to the courts, Borror said.
"We used to have a system where a judge made a decision about an offender's risk to re-offend," she said. "Now it's based only on the offense that they're convicted of, not on any future risk."
The federal law sets a July 2009 deadline for enactment, and threatens states with the loss of federal grant money if they fail to adopt it. In Nevada, officials told lawmakers the state stood to lose $300,000 a year if they failed to adopt the law.