But the chances of courtroom survival for any laws trying to curb such games are not good.
Video games can be intense and extremely violent, and "first person shooter" games are among the most popular. Online retailer Amazon lists five shooter games in its top 10 best selling video games. Americans spend more than $10 billion a year on video games, and more than two-thirds of U.S. households have at least one player of video games, the industry says.
Adam Lanza, 20, the Newtown shooter, "played violent video games for hours at a time," the National Review online reported. "The Columbine killers [two male students who killed 12 other high school students and a teacher before killing themselves] loved 'Doom.' And Anders Breivik [who in 2011 killed 77 people with bombs and weapons in Norway] told a court he played a 'Call of Duty' game to practice his hand-eye coordination."
"The fact of three young men playing video games would not be noteworthy in any other context," National Review author Robert VerBruggen said. "But when mass murderers are at issue, it raises the question of whether our entertainment can affect our behavior, and if so what we should do about it."
He said the validity of a link between violent video games and violent behavior depends on which expert you ask.
Since last Friday's massacre, Sen. Jay Rockefeller, D-W.Va., Sen. Joe Lieberman, Ind-Conn., and Rep. Tim Murphy, R-Pa., among others, have urged Congress to look at whether video games contribute to violence, The Hill newspaper reported.
Lieberman told "Fox News Sunday": "The violence in the entertainment culture, particularly with the extraordinary realism to video games, movies now, etc., does cause vulnerable young men particularly to be more violent."
Rockefeller, Senate Commerce Committee chairman, introduced a bill last week requiring the National Academy of Sciences to investigate any link between violent media, including video games, and violence in the non-virtual world.
Politico said it obtained a copy of Rockefeller's "discussion draft" in which the Federal Trade Commission and the Federal Communications Commission are required to facilitate the NAS study.
Rockefeller, who represents a state where the National Rifle Association wields enormous power, said in a video posted on his official website Congress needs to ban "military-style assault weapons" and "high capacity clips" (magazines). He called for a new initiative on mental health, and said violent images "on television, the Internet or video games can harm and do harm our children's well-being and should be addressed."
Colorado's Democratic Gov. John Hickenlooper has also called for an examination of the link between violent video games and aggression.
The group representing the video game industry, headquartered in Washington, asked last week that any study recognize that research shows little connection between violence and their games, The Washington Post reported.
"The Entertainment Software Association, and the entire industry it represents, mourns the tragedy at Sandy Hook Elementary School," the group said in a statement. "Our heartfelt prayers and condolences go out to the families who lost loved ones, and to the entire community of Newtown. The search for meaningful solutions must consider the broad range of actual factors that may have contributed to this tragedy. Any such study needs to include the years of extensive research that has shown no connection between entertainment and real-life violence."
Christopher J. Ferguson agrees. Writing for Time magazine online, he said, "As a video game violence researcher and someone who has done scholarship on mass homicides, let me state very emphatically: There is no good evidence that video games or other media contribute, even in a small way, to mass homicides or any other violence among youth. Our research lab recently published new prospective results with teens in the Journal of Youth and Adolescence indicating that exposure to video game violence neither increased aggressive behaviors, nor decreased pro-social behaviors.
"Whitney Gunter and Kevin Daly recently published a large study of children in Computers in Human Behavior," he added, "which found video game violence effects to be inconsequential with other factors controlled. And as for the notion of that violent media 'desensitizes' users, recent results published by my student Raul Ramos found that exposure to violence on screen had no influence on viewer empathy for victims of real violence."
Ferguson's analysis carries weight. He is associate professor of psychology and criminal justice at Texas A&M International University, and "has published numerous scientific articles on the topic of video games and mental health and recently served as guest editor for an American Psychological Association's special journal issue on the topic," Time said.
Beyond the problem of linking admittedly violent games to violence in the real world, the legal obstacle to restricting them is enormous, as California found out in the U.S. Supreme Court.
The state had enacted a law, a section of the California Civil Code, that prohibited "the sale of violent video games to minors under 18 where a reasonable person would find that the violent content appeals to a deviant or morbid interest of minors, is patently offensive to prevailing community standards as to what is suitable for minors, and causes the game as a whole to lack serious literary, artistic, political or scientific value for minors."
In other words, the law did not ban sales of violent video games. It banned the sale of such games to minors. Parents, if they wanted, could still buy the game and give it to their children.
The law provided for a penalty of as much as $1,000 per violation -- sale of a violent video game to a minor -- but the penalty applied to businesses and managers, not to sales clerks or anyone who does not have an ownership interest in the business.
California told the Supreme Court in a brief that in enacting the law the Legislature "sought to reinforce the right of parents to restrict children's ability to purchase offensively violent video games. In doing so, the Legislature considered numerous studies, peer-reviewed articles and reports from social scientists and medical associations that establish a correlation between playing violent video games and an increase in aggressive thoughts and behavior, anti-social behavior and desensitization to violence in both minors and adults."
The Legislature also considered the "Federal Trade Commission's report that the video game industry specifically markets M-rated [Mature] video games to minors, that 69 percent of 13- to 16-year-old children were able to purchase M-rated games and that only 24 percent of cashiers asked the minor's age."
A federal judge, citing the First Amendment and using "strict scrutiny," declared the state law unconstitutional and issued a permanent injunction barring its implementation. Violence cannot be considered unprotected speech under the First Amendment without the element of sex, the judge said, even when the restriction is applied to minors.
There are three types of judicial review in determining whether government action is constitutional -- rational basis, intermediate scrutiny and strict scrutiny. Strict scrutiny, the toughest standard, is usually used in First Amendment disputes.
The judge also said the state had failed to show a "causal relationship" between video games and violent behavior, and even if the state had a "compelling interest" to protect minors from violent video games, the law was not the "least restrictive" way to do so -- a requirement under strict scrutiny.
A federal appeals court agreed with the judge, and California asked the Supreme Court for review in an attempt to save the law.
In its brief to the high court, California argued, "Whatever First Amendment value these games may possess for adults, such games are simply not worthy of constitutional protection when sold to minors without parental participation. There is no sound basis in logic or policy for treating offensively violent, harmful material with no redeeming value for children any different than sexually explicit material."
The industry and its allies disagreed.
"The California statute at bar is the latest in a long history of overreactions to new expressive media," the Entertainment Merchants Association said in its brief. "In the past, comic books, true-crime novels, movies, rock music and other new media have all been accused of harming our youth. In each case, the perceived threat later proved unfounded. Video games are no different. They are a widely popular form of expression enjoyed by millions of people. As such, under the First Amendment, they cannot be censored absent the most compelling justification, based on firm evidence of harm, through a narrowly tailored statute where there is no less-restrictive alternative."
A friend-of-the court brief filed in the case by the American Academy of Pediatrics and the California Psychological Association, among others, contended, "Science confirms that violent video games are harmful to minors," citing testimony before Congress by "national experts, medical and mental health professional associations and others, the gist of which is that there is a significant relationship between exposure to media violence and aggressive behavior, and that repeated exposure leads to general increases in aggressiveness over time."
But a coalition including The Motion Picture Association of America, Lucasfilm Ltd., the Directors Guild of America, the Screen Actors Guild and other organizations in the media said in its friend-of-the court brief: "If this [Supreme] Court were to hold that California's statute is valid, it would have a dramatic chilling effect on the motion picture industry," now self-regulated. "If the court's reasoning is not confined to the particular medium of video games, state and local governments could attempt to impose similar restrictions on depictions of violence in other media, including motion pictures. Such restrictions would have an obvious chilling effect, particularly given the inherent amorphousness of restrictions of that type and the potential for a patchwork of nationwide regulation."
"In 1975, a cutting-edge video game console allowed players to bounce an electronic ball back and forth on a television screen by rotating small knobs," another friend-of-the court brief filed by a coalition of states supporting California said. "This was Pong1. Things had changed by 2003." That year, a popular game called Postal2 invited players to:
-- Burn people alive with gasoline or napalm;
-- Decapitate people with shovels and have dogs fetch their severed heads;
-- Beat police to death while they beg for mercy;
-- Kill bald, unshaven men wearing pink dresses (in an "expansion pack" called Fag Hunter);
-- Slaughter nude female zombies;
-- Urinate on people to make them vomit;
-- And shoot players with a shotgun that has been silenced by ramming it into a cat's anus.
"The makers of Postal2 likely never intended its hyperbolic violence to be taken seriously," the brief said. "Ten-year-olds, however, may fail to grasp the satiric content in an exploding cat."
When it ruled in 2011, the U.S. Supreme Court struck down California's ban on the sale of violent video games to minors on free speech grounds by a vote of 7-2, with the majority saying the state law "does not comport with the First Amendment."
An opinion filed by conservative Justice Antonin Scalia said: "Video games qualify for First Amendment protection. Like protected books, plays, and movies, they communicate ideas through familiar literary devices and features distinctive to the medium."
Citing Supreme Court precedent, the opinion said "the basic principles of freedom of speech ... do not vary" with a new and different communication medium."
It added: "This country has no tradition of specially restricting children's access to depictions of violence. And California's claim that 'interactive' video games present special problems, in that the player participates in the violent action on screen and determines its outcome, is unpersuasive."
"Because the act imposes a restriction on the content of protected speech, it is invalid unless California can demonstrate that it passes strict scrutiny -- that is, unless it is justified by a compelling government interest and is narrowly drawn to serve that interest," Scalia said.
"California cannot meet that standard," he added later. "At the outset, it acknowledges that it cannot show a direct causal link between violent video games and harm to minors. Rather ... the state claims that it need not produce such proof because the Legislature can make a predictive judgment that such a link exists, based on competing psychological studies."
One of the two dissenters, Justice Stephen Breyer, said: "This case is ultimately less about censorship than it is about education. Our Constitution cannot succeed in securing the liberties it seeks to protect unless we can raise future generations committed cooperatively to making our system of government work. Education, however, is about choices. Sometimes, children need to learn by making choices for themselves. Other times, choices are made for children -- by their parents, by their teachers and by the people acting democratically through their governments. In my view, the First Amendment does not disable government from helping parents make such a choice here -- a choice not to have their children buy extremely violent, interactive video games, which they more than reasonably fear pose only the risk of harm to those children."