THREE YEARS AGO the Supreme Court decided a set of cases involving state statutes regulating abortion procedures. Roe v. Wade, the original abortion decision handed down in 1973, had authorized state regulation in the second trimester of pregnancy in order to protect maternal life and health, and allowed states to adopt much stronger controls in the third trimester, when a fetus might be viable. In general, the court favored those seeking abortion and discouraged state efforts to make the process more difficult -- emotionally, financially and practically. The justices were particularly critical of laws that they believed had been enacted to impose a significant obstacle to the exercise of a constitutionally guaranteed right.

When the court accepted for argument a case from Pennsylvania raising some of these same issues, many observers concluded that some justices had had a change of heart about state regulation and perhaps about the underlying theory of Roe v. Wade. The Justice Department even filed a friend of the court brief urging the court to overrule its landmark abortion ruling. This would leave decisions on abortion to the individual state legislatures. But last Wednesday's ruling, invalidating the Pennsylvania statutes, was a victory for those who oppose restrictions on abortions, though those who lost the case claim that they will prevail in the long run because they are gaining allies on the court.

* Roe v. Wade was a 7-to-2 decision. Five justices still support that decision and voted last week to strike down the Pennsylvania restrictions. They could even have voted the other way without changing their basic position on abortion. Two of the four who dissented Wednesday had dissented in Roe. The remaining members of the court, the chief justice and Justice O'Connor, would have upheld the Pennsylvania restrictions, but neither indicated a clear disposition to reverse Roe. The chief justice did state his willingness to "reexamine" Roe, but his dissenting opinion is focused on the cases that followed Roe dealing with state regulation, rather than on the basic holding of the 1973 opinion.

The Supreme Court does occasionally reverse an earlier ruling -- most recently in cases involving federal regulation of state employees and race bias in jury selection. But such steps are not taken lightly: they erode confidence in the stability of the law and the value of high court precedent. In the area of abortion rights, there are still no clear signs that, even with a couple of changes in the court, such a drastic step is in the cards.