If you're trying to win a First Amendment case at the Supreme Court, your best bets are to be really political, or really offensive.

And if you lose Chief Justice John Roberts, you almost certainly will lose your case.

In the 10 years since he joined the Court, Roberts has established himself as the central arbiter of important First Amendment issues. By a long shot, Roberts writes more of the Court's free-speech decisions than any of his colleagues. And even when he doesn't write the rulings, he always is in the majority—literally. Roberts is the only justice who has never been in the minority on a major free-speech case.

"This is an area he has carved out for himself," said Ronald Collins, a law professor at the University of Washington who has studied the Roberts Court and free speech. "For the time being, one thing is certain: He is the go-to person on the First Amendment."

By Collins' count, the Court has decided 38 cases on First Amendment free-expression issues since Roberts became chief justice. Roberts has written 13 of those rulings; no other justice has written more than five, Collins said.

That number will likely climb to 39 this month, when the Court is expected to rule in a case challenging Texas' refusal to print the Confederate flag on specialty license plates.

As a rule, Roberts usually is protective of the First Amendment. Laws that encroach on free speech—whether the speech in question is a campaign donation or a video of animal cruelty—have fared poorly under Roberts.

Yet there are glaring exceptions, in both directions, that make the chief justice difficult to predict.

Roberts defied many First Amendment experts' expectations in April, when he cast the deciding vote to uphold a Florida law barring judicial candidates from personally soliciting campaign contributions. There aren't many restrictions on speech Roberts likes—and campaign-finance law seemed like an especially unlikely place to find one.

That decision was a stark departure from the Court's past campaign-finance cases—the area where Roberts has pressed his First Amendment case most aggressively. Since 2007, there have been five 5-4 rulings striking down campaign-finance laws, including Citizens United. Roberts wrote three of them.

"If the First Amendment protects flag burning, funeral protests and Nazi parades—despite the profound offense such spectacles cause—it surely protects political campaign speech despite popular opposition," he wrote last year in McCutcheon v. FEC.

And indeed, Roberts' most prominent free-speech decisions are hardly limited to campaign-finance law. In 2010, he wrote the Court's 8-1 decision striking down a federal law that banned the sale of animal "crush" videos, rejecting the government's argument that extreme animal cruelty has no value to society and therefore is not entitled to First Amendment protection.

A year later, he sided with the Westboro Baptist Church, the fundamentalist organization known for picketing military funerals with antigay placards and chants.

"Speech is powerful. It can stir people to action, move them to tears of both joy and sorrow, and—as it did here—inflict great pain," Roberts wrote. "On the facts before us, we cannot react to that pain by punishing the speaker. As a Nation we have chosen a different course—to protect even hurtful speech on public issues to ensure that we do not stifle public debate."

Justice Samuel Alito, who joined the Court just a few months after Roberts, was the only dissenting justice in the animal-cruelty and Westboro Baptist cases. Outside the context of campaign-finance reform, Roberts has been surprisingly able to corral unanimity even in polarizing free-speech cases.

Collins pointed to a case last year in which the Court ruled unanimously against Massachusetts' "buffer zones," which outlawed protests within 35 feet of abortion clinics. It was a unanimous decision in an abortion case, and all of the liberal justices simply signed on to Roberts' decision—they didn't even write separate opinions agreeing with the outcome but explaining different rationales.

"I thought this was Roberts at his masterful best. I mean, nobody could have predicted a 9-zip judgment in that case," Collins said.

Roberts also was in the majority, though he didn't write the decisions, in the Court's rulings against laws that criminalized lying about military awards or banned violent video games.

But he has also sided against several First Amendment claims, denying free-speech protections in certain circumstances to government employees, inmates, and students.

"The pattern is uniform and troubling: when the government is functioning as an authoritarian institution, freedom of speech always loses," Erwin Chemerinsky, the dean of the law school at the University of California, Irvine, wrote in a 2011 law review article.

Chemerinsky also noted a 2010 decision—written by Roberts—in which the Court ruled against American advocacy organizations that trained groups designated as terror groups on how to use peaceful alternatives, such as the United Nations, to resolve disputes. The Court said the government could punish those organizations for communicating with terrorist organizations, even if they were not aiding or encouraging terrorism.

"The Court allowed the government to prohibit speech that in no way advocated terrorism or taught how to engage in terrorism solely because the government felt that the speech assisted terrorist organizations. "¦ The deference that the Court gave to the government was tremendous and the restrictions it placed on speech were great," Chemerinsky wrote.

And while the Court has used the First Amendment to roll back campaign-finance laws, protecting freedom of speech was simply the rationale—not the primary motivation—he said.

"Some Roberts Court decisions have been protective of speech. "¦ But a look at the overall pattern of Roberts Court rulings on speech yields a clear and disturbing conclusion: it is not a free speech Court," Chemerinsky wrote.

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