The Supreme Court’s 9-0 decision Monday in Shurtleff v. Boston, the City Hall Plaza flagpole case, marked the third time in recent memory that the high court ruled unanimously that free speech rights in Boston and Massachusetts had been suppressed in violation of the Constitution.

In the 1995 case of Hurley v. Irish-American Gay, Lesbian, and Bisexual Group of Boston, the private organizers of the city’s annual St. Patrick’s Day parade turned down an Irish gay-pride group that wanted to carry a banner in the parade. The group, known as GLIB, sued for the right to march, arguing that the parade’s organizers had no legal right to exclude them. Every Massachusetts court, up to and including the Supreme Judicial Court, ruled in GLIB’s favor and said the parade organizers were obliged to accommodate them.

But when the case reached the nation’s highest court, all nine justices agreed that Massachusetts was wrong. Under the First Amendment, the organizers of a private parade could not be compelled to admit a group whose message they chose not to promote. Fundamental to “the principle of free speech is that one who chooses to speak may also decide what not to say,” wrote Justice David Souter. Massachusetts, the court held, “is not free to interfere with speech for no better reason than promoting an approved message or discouraging a disfavored one.”

Then there was the case of McCullen v. Coakley, which challenged a Massachusetts law requiring opponents of abortion to stay at least 35 feet away from the entrance to any abortion clinic. The law made it a crime, punishable by fines and imprisonment, to speak, pray, or hold a sign within that “buffer zone” — even on a public sidewalk. Once again the Massachusetts courts, applauded by much of the state’s political and media establishment, upheld the violation of free speech. Once again the US Supreme Court unanimously overruled them. All nine justices agreed that the Massachusetts law was repugnant to the First Amendment. Even the court’s staunchest defenders of abortion rights — three of them women — emphasized that citizens have a right to express their views on public sidewalks.

Now, in yet another unanimous decision, the high court has admonished public officials in Boston for contravening the free speech rights of a group whose message they didn’t care for.

For a dozen years, city officials had routinely allowed private organizations to hold hundreds of ceremonies on City Hall Plaza, always permitting them to raise any flag they wished on a flagpole that Boston had explicitly designated a “public forum.” But when Harold Shurtleff, who heads a civic group called Camp Constitution, tried to schedule an hour-long ceremony to “commemorate the civic and social contributions of the Christian community” while flying a Christian flag, the city said no. This was the only time the city had denied a flag request, and its reason for doing so was clear: City Hall rejected Camp Constitution’s application, wrote Justice Stephen Breyer in his opinion, because of “the fact that it was the Christian flag.” In so doing, Boston “discriminated based on religious viewpoint and violated the Free Speech Clause.”

Any one of these cases might have reflected honest confusion among Boston or Massachusetts officials about their constitutional obligation to protect freedom of expression. Three such cases point to a more serious problem. All three times, the power of the state, either legislative or judicial, was deployed to suppress a conservative and/or religious point of view. The parade organizers didn’t want to celebrate LGBT pride. The prolife protesters wanted to recommend alternatives to abortion. Camp Constitution wanted to honor the role of Christianity in Boston history. Each time, the muscle of the government was flexed to keep the viewpoint from being expressed. And members of Boston’s influential liberal elite, with rare exceptions, either said nothing or endorsed the infringement of the conservatives’ First Amendment liberties.

There have been other recent examples of Boston authorities attacking the right of an unpopular minority to engage in free expression.

Perhaps the most egregious occurred in August 2017, when a small group of little-known libertarians and eccentrics secured a permit to hold what they billed as a “Free Speech Rally” on Boston Common. The group posed a threat to no one. But their rally took place a week after the “Unite the Right” march of white supremacists in Charlottesville, Va., degenerated into deadly violence and there was a rumor something similar was planned for Boston. At a press conference with other elected officials, Boston Mayor Marty Walsh amplified the rumor and denounced the organizers of the minuscule rally. “Boston does not want you here,” he declared, vowing to do everything he could to shut down the event.

In the end, the rally took place but the handful of speakers on the Parkman Bandstand were prevented from being heard. They were segregated behind a 225-foot buffer zone and uniformed officers made sure no one got close enough to listen to them. A directive from the Boston Police Department barred even reporters from approaching the speakers.

As a result, the members of the little rally “spoke essentially to themselves for about 50 minutes,” the Globe reported. The city’s “security measures denied them an audience as well as press coverage of what they had to say.” When the city’s police commissioner, Bill Evans, was later asked if it had been right to treat them that way, he unapologetically pronounced it “a good thing,” adding: “Their message isn’t what we want to hear.”

The whole episode was shameful — another case in which the free-speech rights of a disfavored Boston minority were trampled underfoot by local government.

For much of the 19th and 20th centuries, the phrase “banned in Boston” evoked the right-wing Puritanism of the city’s political leadership. Today Boston and Massachusetts are left-wing bastions, yet the willingness to stifle unpopular expression persists. All that has changed is that those censored now are likely to be politically or religiously conservative. That — and the fact that the justices of the Supreme Court, liberals and conservatives alike, are far more vigilant about upholding freedom of speech. How many more times must Boston be spanked by all nine members of the nation’s highest court before it learns to treat the First Amendment with respect?