The Supreme Court struck down as unconstitutional yesterday an Indianapolis law, similar to ones proposed in nearly a dozen cities, that sought to ban pornography on the grounds that it discriminated against women by portraying them as sex objects.

The court took the unusual action of summarily affirming, without argument, an appeals court ruling in August that struck down the statute as "thought control."

The court also refused to block the extradition to Israel of John Demjanjuk, accused of murdering thousands of Jews as operator of the gas chamber at the Treblinka concentration camp in Poland.

The court also agreed, as expected, to hear oral arguments April 23 on the constitutionality of a key provision of the Gramm-Rudman-Hollings deficit-reduction law. The court's ruling is expected by July.

And in another ruling, the court gave a green light to the growing "no pass-no play" movement that would require students to meet minimum academic standards to participate in school sports or other activities. The limited ruling said simply that the court saw no substantial constitutional issues.

The Indianapolis pornography case, Hudnut v. American Booksellers Association Inc., has been closely watched by other cities weighing laws to battle the $8 billion-a-year pornography industry. A similar measure has twice been adopted in Minneapolis, but was vetoed each time by the mayor.

Unlike typical pornography laws that focus on the explicit nature of sexual activity, the Indianapolis statue linked pornography to violent crime against women, and said it violated their civil rights. It allowed any woman who says she has been harmed because of the material to seek damages from businesses that sell or exhibit it.

The law, passed in 1984 but stayed by the courts, forged unusual alliances, with religious conservatives and radical feminists supporting it and librarians, booksellers and civil liberties groups lined up against it. A U.S. District Court judge ruled the law violated free speech rights.

A Chicago federal appeals court panel, in a ruling by a Reagan-appointed conservative, said the statute violated constitutional free-speech protections.

Judge Frank Easterbrook said that under the Indianapolis law, "speech treating women in the approved way -- in sexual encounters 'premised on equality' . . .-- is lawful no matter how sexually explicit. Speech treating women in the disapproved way -- as submissive . . . or enjoying humiliation -- is unlawful no matter how significant the literary, artistic or political qualities of the work taken as a whole.

"The state may not ordain preferred viewpoints in this way. The Constitution forbids the state to declare one perspective right and silence opponents," Easterbrook said.

Chief Justice Warren E. Burger and Justices William H. Rehnquist and Sandra Day O'Connor said they wanted to hear oral argument in the case but gave no indication which way they would have ruled. As a summary affirmance, the court's action yesterday was unaccompanied by an opinion. But it becomes the law nationwide, unlike instances in which the court simply allows a lower court judgment to stand.

In the Gramm-Rudman-Hollings case, the justices will hear appeals from a special three-judge federal court ruling earlier this month that struck down as unconstitutional the heart of the law -- the "automatic trigger" provision in which across-the-board spending cuts would automatically occur if Congress and the president could not meet the deficit targets set by Gramm-Rudman-Hollings. The three-judge panel said the law violated the Constitution's separation of powers doctrine by giving the Comptroller General, who is under the control of Congress, executive branch functions in carrying out the cuts.

The justices said each side could argue for one hour, twice the normal amount allotted. The first $11.7 billion in spending cuts under the law, due to take effect Saturday, were not affected by the panel's ruling. The cases are Bowsher v. Synar, U.S. Senate v. Synar and O'Neill v. Synar.

In the school sports case, Stamos v. Spring Branch Independent School District, the justices dismissed a challenge to a Texas law barring high school students from extracurricular activities unless they pass all courses.