Anti-abortion protester Eleanor McCullen, of Boston, standing at the painted edge of a buffer zone outside a Planned Parenthood location in Boston in December of 2013. (AP Photo/Steven Senne)

The Supreme Court on Thursday struck down so-called "buffer zones" around abortion clinics in Massachusetts, unanimously ruling that the 2007 state law creating them violates the free-speech rights of anti-abortion advocates who wish to counsel patients on their way inside.

The buffer zones extended 35 feet from the entrance or driveway of reproductive health facilities, effectively encompassing private property and public sidewalks alike. The law prohibited people from lingering in those zones unless they were employees of the facilities, patients on their way in or out, or first responders, law enforcement or other public workers with a reason to be there. Anyone who happened to be walking by could travel these sidewalks, too — "solely for the purpose of reaching a destination other than such facility.”

Although their reasoning differed (the nine justices produced three opinions), the court unanimously agreed that Massachusetts could not limit the First Amendment rights of people wishing to weigh in on a matter of unquestionable public debate on a public forum like a sidewalk. Chief Justice John Roberts' majority opinion, in fact, makes a rousing defense of the sidewalk itself as one of the last remaining places in the Internet Age — in the era of the Filter Bubble, Fox News and the Big Sort — where free speech might actually encounter a dissenting audience:

It is no accident that public streets and sidewalks have developed as venues for the exchange of ideas. Even today, they remain one of the few places where a speaker can be confident that he is not simply preaching to the choir. With respect to other means of communication, an individual confronted with an uncomfortable message can always turn the page, change the channel, or leave the Web site. Not so on public streets and sidewalks. There, a listener often encounters speech he might otherwise tune out. In light of the First Amendment’s purpose “to preserve an uninhibited marketplace of ideas in which truth will ultimately prevail,” ...this aspect of traditional public fora is a virtue, not a vice.

The ruling also makes a compelling case that sidewalks are different from bullhorns, that they allow a uniquely valuable form of speech: namely, the kind of close-quarters conversation between two people that might actually change minds. The plaintiffs in the case argued that the 35-foot buffer zones prevented them from engaging in precisely the kind of speech they sought. They wanted to have intimate conversations with women on their way into these clinics. They wanted to get close enough to place a pamphlet in an open hand.

Both forms of expression — normal conversation and leafletting — have "historically been more closely associated with the transmission of ideas than others," Roberts writes. And shared public space is central to both:

Respondents also emphasize that the Act does not pre­vent petitioners from engaging in various forms of “pro­test”—such as chanting slogans and displaying signs— outside the buffer zones. That misses the point. Petitioners are not protestors. They seek not merely to express their opposition to abor­tion, but to inform women of various alternatives and to provide help in pursuing them. Petitioners believe that they can accomplish this objective only through personal, caring, consensual conversations. And for good reason: It is easier to ignore a strained voice or a waving hand than a direct greeting or an outstretched arm.