The South Dakota Legislature has passed a law that is unconstitutional under current Supreme Court doctrine, and Gov. Mike Rounds has signed it.

The law would ban abortions, except when necessary to save the life of the mother. It directly contradicts the U.S. Supreme Court's ruling in Roe vs. Wade (1973), reaffirmed in Planned Parenthood vs. Casey (1992), that a pregnant woman has a right to choose to have an abortion.

Q: Why pass a law that you know is unconstitutional?

A: The Legislature expects the law to give the Supreme Court an opportunity to overturn Roe, making an abortion ban constitutional.

Q: If the plan succeeds, would abortion be banned nationwide?

A. No. It would mean they would be banned in South Dakota and six other states: Arkansas, Illinois, Kentucky, Louisiana, Missouri and Montana. Those states have passed so-called trigger laws, which would automatically ban abortion if Roe is overturned. Several more states are following South Dakota's lead and passing abortion bans that contravene Roe. If Roe is overruled, the legislatures of the other states, including Minnesota, would be free to ban abortions, keep them legal, or regulate and restrict them in new ways.

Q: Will the plan succeed?

A: Probably not, unless there is a change in the Supreme Court's makeup. It would take five justices to overturn Roe. Two justices, Antonin Scalia and Clarence Thomas, have clearly indicated a readiness to vote that way. The two newest justices, Chief Justice John Roberts and Justice Samuel Alito, are conservatives, and abortion opponents have high hopes that they will vote with Scalia and Thomas. Alito and Roberts got through their confirmation hearings without saying how they would rule if a fundamental challenge to Roe comes before them.

But the other five justices have affirmed Roe or have indicated a willingness to do so. Four of those five -- Justices Stephen Breyer, Ruth Bader Ginsburg, David Souter and John Paul Stevens -- appear solidly in the pro-Roe camp. Justice Anthony Kennedy voted to affirm Roe in the 1992 Casey ruling, but many court analysts believe he is wobbliest of the pro-Roe camp.

Some, such as Leslee Unruh of Sioux Falls, S.D., one of the leaders behind the South Dakota abortion ban, believe the court might find the ban constitutional, even without any change in personnel. But most Supreme Court analysts say there are still five votes to sustain Roe.

Q: So why are the South Dakota legislators doing this?

A: They hope that by the time the court reviews their new law, the court makeup will have changed. This is based on several premises, none of them certain. But unless Kennedy changes his position, the scenario comes down to this: the two new justices are ready to overturn Roe and -- between now and the time the South Dakota law is argued at the Supreme Court -- at least one of the pro-Roe justices has been replaced with another justice ready to vote against Roe.

"They seem to be betting on several things," said law Professor Thomas Berg of the University of Thomas, "how the new justices will vote, who will retire, who will replace them, how that person will vote and when all this will occur. And none of those bets are sure things."

Q: Why do they think they will win all those bets?

A: The bill's chief sponsor, Rep. Roger Hunt, has said the possible retirement of Stevens, 85, who supports Roe, makes it a "very real and very viable" possibility that by the time the South Dakota law makes it way to the court, a fifth vote to overturn Roe will have arrived on the scene.

But close Supreme Court watchers say that despite his advanced age, Stevens appears to be in good health and enjoying his work after 30 years on the court. Further, since Stevens is among the most liberal and most reliable abortion rights supporter on the court, there's little reason to assume that he would hasten his retirement at a time when Republicans control the White House and the Senate.

Of course, if Stevens or another of the pro-Roe justices developed a health problem while the South Dakota law is making its way through the lower courts, that could trump such political considerations.

Q: How long will take to make its way to the Supreme Court?