The majority opinion he wrote upholding the federal Partial-Birth Abortion Ban Act offers hope both for those who think the impact of Wednesday's decision will be limited and for those who think it will be profound.
While Kennedy adopted some language favored by abortion opponents - "life of the unborn," "abortion doctor," "respect for life" - he also carefully distinguished the controversial procedure that was the focus of the Supreme Court case from a more common abortion method used after 12 weeks of pregnancy. The latter was unaffected by the ruling.
There was widespread agreement that the court's ruling was important, upholding for the first time a nationwide ban on a controversial abortion procedure. The key difference from earlier rulings was in personnel, with Justice Samuel Alito replacing Justice Sandra Day O'Connor.
The majority - Chief Justice John Roberts, Justice Antonin Scalia, Justice Clarence Thomas, Alito and Kennedy - consists of five Catholics who were appointed by Republican presidents who believed Roe v. Wade was wrongly decided and should be overturned.
For the moment, though, Kennedy holds the balance of power. He has written key decisions on both sides of the long-standing divisive issue.
Particularly since O'Connor's retirement last year, what he thinks probably is where the court will come out when asked to consider new abortion restrictions enacted either by states or Congress.
Ed Whelan, a former law clerk to Scalia and later an official in the Bush administration Justice Department, said the decision most likely would invite new state laws banning the same procedure covered by the federal law and requiring that women seeking abortions be given detailed warnings about the dangers of terminating their pregnancies.
"Those regulations seem to me far more likely to be sustained," Whelan said.
But David Garrow, a Cambridge University historian who has written about the court, said the prospect of reducing the availability of abortion is remote, based on Kennedy's opinion.
"I not only don't think that the Kennedy opinion illuminates a path towards doing that, I actually think it creates obstructions, serious obstructions," Garrow said.
By contrast, Roger Evans, public policy director at the Planned Parenthood Federation of America, said Kennedy opened the door to wide-ranging restrictions and, perhaps as importantly, signaled abortion opponents that they should test the limits of the constitutional right to an abortion that the court established in 1973.
Evans pointed to the court's about-face regarding the necessity of carving out an exception if the procedure is necessary to protect a woman's health. In past decisions, medical uncertainty on this topic was resolved in favor of allowing the procedure to be performed.
Kennedy changed that standard Wednesday. "Where there is medical disagreement, the tie no longer goes to protecting women's health," Evans said. "That's a troubling green light."
Prominent abortion opponents also suggested the door was open to more aggressive action.
Troy Newman, president of the anti-abortion group Operation Rescue in Wichita, Kan., said: "This is a new day in the abortion battle. After 34 years of innocent children dying throughout the country we now have a new court, led by Chief Justice John Roberts, that has a plan to end abortion in America."
Evans, an abortion-rights supporter, said the most salient common trait of the five-justice majority is that they were chosen by GOP presidents who oppose abortion. Whelan, an abortion opponent, said the majority deferred to a democratically elected Congress. "They were not imposing their own views," he said. "It would seem to me that their religious faith was irrelevant."