They celebrated outside the Supreme Court after Monday’s surprise decision reaffirming abortion rights. They danced to Michael Jackson (“I want to love you . . .”), as they had earlier to the Spice Girls and to Harry Belafonte’s “Jump in the Line.”

In the front row, facing the marble temple, a young woman held up a homemade sign:

“Roses are red

Violets are blue

Abortion is legal

So f--- you.”

Justice Anthony Kennedy didn’t use those words, but that was, essentially, the valentine he delivered to the antiabortion movement. The justice, siding with the liberal bloc, lent his name to Justice Stephen Breyer’s resounding defense of abortion rights in his 5-to-3 majority opinion. In doing so, Kennedy put an end to any thought of banning abortion in America anytime soon — even if a future Republican president names a conservative to fill the late Antonin Scalia’s seat.

The Republican-controlled Senate refuses to consider President Obama’s nominee, Merrick Garland, but a fifth liberal justice has arrived anyway. Kennedy, a Reagan appointee and the longest-serving current justice, surprised many last week by joining the liberals in defending race-based affirmative action. In earlier terms, he provided the key vote in legalizing same-sex marriage.

It’s not that Kennedy has become a bleeding heart (he sides with the conservatives on gun rights, campaign finance and Obamacare) but that he has split with conservative colleagues such as Samuel Alito who, by temperament, are disinclined to find consensus.

You could see it Monday morning in the chamber, where, for the second week in a row, Alito took the unusual step of reading aloud from his dissent in a case that found Kennedy on the opposite side.

While Breyer read the majority opinion in the abortion case, Alito was a study in agitation. He shook his head, raised his eyebrows, clenched his jaw, rocked in his chair and carried on a silent conversation with himself — apparently rehearsing, in his head, his dissent.

When Breyer finished, Alito pulled up his microphone and delivered a bitter rebuttal, even citing Breyer by name. He had the acidity of Scalia’s legendary dissents, but he lacked Scalia’s neutralizing humor: “No justification. . . . Obviously wrong. . . . Contrary to a cardinal rule. . . . This is an abuse of our authority. The majority in this case has not done what a court of law must do.”

Pro-choice supporters celebrated while pro-life advocates protested the Supreme Court's decision to strike down a Texas law imposing strict regulations on abortion providers June 27. (Reuters)

Alito informed his colleagues that they violated the concept of res judicata (claim preclusion), then added: “Res judicata predates the founding of the country. That’s why it’s in Latin.”

During this performance, Kennedy sat calmly, reading and rocking gently at times. But mostly he sat, lips pursed, staring directly ahead of him — as still and silent as the stone likenesses of Hammurabi, Moses, Solomon and Confucius on the frieze above him.

He’s no King Solomon, but Kennedy, the perpetual swing vote, may be the dominant lawgiver of his day. Unlike Alito and Clarence Thomas (and, to a lesser extent, Chief Justice John Roberts), he recognizes the importance of public consensus on cultural issues, such as the growing acceptance of gay marriage. On abortion, which chronically divides Americans, Kennedy has avoided destabilizing change.

“No one who follows the Court can doubt that he finds abortion very troubling,” the Atlantic’s Garrett Epps wrote earlier this year. “. . . But no one also doubts that Kennedy takes the Supreme Court, and its place at the center of American law, seriously as well. His head here may conflict with his heart.”

In Whole Woman’s Health v. Hellerstedt — the Texas case, decided Monday, that would have forced abortion clinics to close by imposing near-impossible restrictions on them — the appellate court brazenly ignored the 1992 Planned Parenthood v. Casey decision, which Kennedy co-wrote. He was having none of it. He didn’t merely agree to strike down the law on technical grounds; he joined a full-throated affirmation of abortion rights.

Justice Elena Kagan looked toward the press and gave a satisfied smile as Breyer said they had declared the Texas law unconstitutional because it imposed an “undue burden” on abortion seekers. Breyer ridiculed the idea that abortion needed stricter regulations than procedures such as childbirth (which is 14 times as deadly), colonoscopies (10 times as deadly) and liposuction (28 times as deadly).

Alito was grim. Leaning forward, his lower jaw protruding, he informed the majority that they are encouraging the view that “if at first you don’t succeed, sue, sue again.” He said that the sort of thing that occurred in the case could have qualified as “abusive litigation.” He accused the majority of being lazy and of ignoring “the normal rules.”

His discouragement is understandable. The Senate’s refusal to confirm Garland was supposed to prevent a liberal majority on the court. But, somehow, it happened anyway.

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