PIERRE, S.D. — A federal judge late yesterday blocked a South Dakota abortion bill from becoming law today, tentatively ruling that the measure is an unconstitutional violation of free speech.

The legislation would have required abortion doctors to inform women that abortion ends the lives of "human beings" and poses various medical and psychological risks. Failure to give the informed-consent warning could have resulted in 30 days in jail and a $200 fine.

U.S. District Judge Karen Schreier of Rapid City ruled that Planned Parenthood of Minnesota, North Dakota and South Dakota, which sued the state, has shown it has a fair chance of winning on its claim that the proposed law infringes on the First Amendment rights of doctors.

The measure would make a doctor inform a woman that she has a legal relationship with her unborn child and the relationship will be terminated by an abortion, which will end the life of that "human being."

"The South Dakota statute requires abortion doctors to enunciate the state's viewpoint on an unsettled medical, philosophical, theological and scientific issue — that is, whether a fetus is a human being," the judge wrote in an order granting Planned Parenthood a preliminary injunction.

"The informed consent provisions of the statute are unconstitutional compelled speech rather than reasonable regulations of the medical profession," Schreier continued. "The amendments to the South Dakota informed consent provisions go much further than ... other cases reviewing similar statutes, and force abortion doctors to inform women that abortion will terminate the life of a whole, separate, unique, living human being," the judge wrote.

The federal judge also said the proposed law discourages doctors from expressing views that contradict the state's message.

"South Dakota may not ... violate the First Amendment rights of abortion providers by compelling them to espouse the state's theology," Schreier said.

State lawyers had argued that the required information is medically accurate and supported by science. The proposed law does not curb reasonable access to abortions in South Dakota, they added.

In stopping the legislation from becoming law today, Schreier said South Dakota already has a robust law that requires a woman to be informed that abortion involves termination of an unborn child's life and that there are medical risks. The existing law remains in effect, she said.

The judge heard arguments on June 29 on the request for a temporary injunction. A hearing is set for October on Planned Parenthood's request for a permanent order barring the state from enacting the proposed law.

Planned Parenthood lawyers said the measure, passed by the 2005 Legislature, was ideological and too vague, adding that doctors should not be forced to become mouthpieces for the state.

State lawyers, however, said requiring doctors to tell patients that factors such as depression and suicide could occur after abortions is, in fact, based on science.

Abortion has been legal since a 1973 U.S. Supreme Court ruling. However, the high court has said states may place reasonable restrictions on abortion.

The state may express its preference for childbirth over abortion by requiring a woman to be informed about available information on fetal development and the assistance that may be available if she decides to have her baby, Schreier said.