"Prior to Roe," said David Garrow, a law professor at Cambridge University, and a longtime Supreme Court scholar, "whether one could obtain a legal abortion in the face of an unwanted pregnancy was a crapshoot. For 30 years now, it's been a constitutionally guaranteed right."

But the ruling was a qualified one, as many anti-abortion supporters have noted over the years, and that fact has been used by them in their efforts to narrow the scope of other abortion provisions. Blackmun noted the state's "important interests in safeguarding health, maintaining medical standards, and protecting potential life" are compelling enough to justify regulation "at some point in pregnancy."

They found success last year when the justices in a sharply divided 5-4 ruling upheld a federal ban on a controversial a late-term procedure, rejecting concerns the law didn't take into account the physical safety of the mother.

The swing vote, as in previous cases, came from Kennedy. In angry dissent, Justice Ruth Bader Ginsburg, the lone woman on the high court since O'Connor stepped down, called the majority's conclusions "alarming" and said they "cannot be understood as anything other than an effort to chip away a right declared again and again by this court, and with increasing comprehension of its centrality to women's lives."