Here’s a breakdown of the arguments that mattered to the Supreme Court in its decision today to strike down California’s law banning the sale of violent video games to minors. The court voted 7-2 in favor of holding the law as unconstitutional on First Amendment grounds. It’s interesting to see how the court considered the evidence and decided.

The divided vote shows that this wasn’t an overwhelming victory for the video game industry and free speech advocates. In the 92-page decision, here are the arguments that stand out on both sides.

— Writing for the majority, Justice Antonin Scalia noted that previous cases have held that “the basic principles of freedom of speech do not vary with a new and different communication medium.”

— Opponents of violent video games foundered in their attempts to define violence. Scalia noted that Dante’s Inferno and the Grimm’s Fairy Tales depict violent scenes but have never been restricted. “Reading Dante is unquestionably more cultured and intellectually edifying than playing Mortal Kombat. But these cultural and intellectual differences are not constitutional ones. Crudely violent video games, tawdry TV shows, and cheap novels and magazines are no less forms of speech than The Divine Comedy.””

— Scalia said the court found unpersuasive the state’s claim that video games are special because players participate in the interactive act of violence. The state failed to justify singling out video games in arguing for a “compelling government interest” in the restrictions. Scalia said that psychological studies purporting to show a connection between “exposure to violent video games and harmful effects on children do not prove that such exposure causes minors to act aggressively,” as the effects are small and indistinguishable from the effects produced by other media.

— Justice Scalia stated with regard to the validity of the scientific evidence put forth, “The State’s evidence is not compelling. California relies primarily on the research of Dr. Craig Anderson and a few other research psychologists whose studies purport to show a connection between exposure to violent video games and harmful effects on children. These studies have been rejected by every court to consider them, and with good reason: They do not prove that violent video games causeminors to actaggressively (which would at least be a beginning). Instead, ‘[n]early all of the research is based on correlation, not evidence of causation, and most of the studies suffer from significant, admitted flaws in methodology.'”

— Scalia said the game industry’s existing voluntary rating system accomplishes the goal of giving parents a choice about whether to restrict their children’s access to violent games

Justices Samuel Alito and John Roberts concurred with the majority, but issued their own opinion.

— Justice Alito’s opinion opened with a comment on how the effects of new technology are unpredictable. He noted that spending hours controlling the actions of a character who guns down innocent victims might actually be different in kind from reading a description of violence in a work of literature. He found the increasing realism of violent games to be disturbing. Motion-sensing systems (such as Microsoft’s Kinect) can now enable players to mimic violent actions to produce a violent effect on the screen, like swinging a baseball bat to “smash a skull.”

— “These present-day and emerging characteristics of video games must be considered together with characteristics of the violent video games that have already been marketed,” Alito said. “In some of these games, the violence is astounding.”

Justices Stephen Breyer and Clarence Thomas dissented. They used the following arguments.

— Breyer said that it is possible to define violent games that are the most realistic and potentially damaging. He found California’s description of violence with words such as “kill,” “maim” or “dismember” to be precise enough to be enforced, much like the term “nudity” in anti-obscenity laws. Breyer said that evidence submitted by California about the effects of violent video games on children was more extensive than that submitted for obscenity laws.

— “The statute prevents no one from playing a video game, it prevents no adult from buying a video game, and it prevents no child or adolescent from obtaining a game provided a parent is willing to help,” Breyer wrote. “All it prevents is a child from buying, without a parent’s assistance, a gruesomely violent video game of a kind that the industry itself tells us it wants to keep out of the hands of those under the age of 17.”

— Breyer wrote, “What sense does it make to forbid selling to a 13-year-old boy a magazine with an image of a nude woman, while protecting a sale to that 13-year-old of an interactive video game in which he actively, but virtually, binds and gags the woman, then tortures and kills her? What kind of First Amendment would permit the government to protect children by restricting sales of that extremely violent video game only when the woman — bound, gagged, tortured and killed — is also topless?”

— Breyer also argued, “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.”

— Thomas argued that parents have authority over children and can thus control what speech their children hear or see. He says there is a long tradition behind that belief and that video game publishers do not have the unfettered right to speak to children without restraints. He noted that the law does not ban the sale of violent games to minors; rather, the law does allow parents to buy violent games for minors if they so choose.