WASHINGTON -- If John G. Roberts Jr. is confirmed for a seat on the U.S. Supreme Court, he will be confronted with a number of highly controversial issues on which his vote could make a difference and could reveal what kind of justice he will be.

Will he be a justice in the strict-constructionist mold of Antonin Scalia and Clarence Thomas, as many conservatives believe, or a pragmatic conservative like Sandra Day O'Connor, as liberals hope?

The docket for the court's 2005-06 term, which begins Oct. 3, includes cases dealing with abortion rights, discrimination against homosexuals and the relationship between state and congressional authority. Other issues, such as the constitutionality of a federal law prohibiting "partial-birth" abortions and the procedures used to try suspected "enemy combatants" in the war on terror, may be added.

Speculation about Roberts is complicated by his short tenure on the U.S. Court of Appeals for the District of Columbia Circuit, where he has served since 2003, and by the fact that some of the positions he embraced as a lawyer in the Reagan and first Bush administrations may not reflect his own views.

Supreme Court experts also caution that it often takes a new justice a while to find a voice.

"With regard to a justice's judicial philosophy evolving, you have to look at the long term and not just the first year," said David M. O'Brien, a University of Virginia political scientist.

O'Brien noted that the views of O'Connor, whom Roberts would replace, changed over time.

"Increasingly, she paid much more attention to the impact of Supreme Court decisions on the daily lives of citizens, such as when it came to drug testing or arresting a person for a minor traffic violation. I suspect Roberts is going to be very low-key at first, independent but generally aligned with Scalia and Thomas and [Chief Justice William H.] Rehnquist. I think we'll be talking about Justice [Anthony] Kennedy as the swing vote on the court."

So far the high court has accepted 37 cases for review in the 2005-2006 term. Following are some of the most significant in which Roberts' vote could be pivotal.

Abortion rights
On Nov. 30 the court will hear arguments in two abortion cases.

In Ayotte v. Planned Parenthood, it will decide the constitutionality of a New Hampshire law requiring parents be notified if a minor seeks an abortion. The 1st U.S. Circuit Court of Appeals in Boston blocked the law because it didn't contain an exception to protect the health of the woman.

The second abortion case, Scheidler v. National Organization for Women, is the third installment of a legal dispute stretching back to the 1980s over whether NOW and abortion clinics can sue violent protesters at clinics under a federal racketeering law.

In 1994, the court ruled that NOW and clinics could sue anti-abortion groups, including Operation Rescue and the Pro-Life Action Network, under the Racketeer Influenced and Corrupt Organizations Act, or RICO, even if the activists didn't have an economic motive for their tactics. But in 2003 the court threw out a racketeering judgment on the grounds that the protesters' acts, however violent or intimidating, did not involve robbery or extortion, the main elements of a federal law called the Hobbs Act that the clinics had cited in their lawsuit.

Anti-abortion activists hailed the 2003 decision as a complete victory, but the 7th Circuit Court of Appeals in Chicago instead concluded that four of the violent or threatening acts ascribed to the protesters might still amount to a violation of the Hobbs Act. Joseph Scheidler, one of the anti-abortion activists, asked the Supreme Court to return to the case and repudiate the 7th Circuit's interpretation.

O'Connor was in the majority in both of the previous incarnations of Scheidler v. NOW.

Federal v. state's rights
Justice O'Connor has been one of the "Federalism Five" on the high court who threw out two federal laws for violating state's rights -- a statute banning the possession of guns near schools and a portion of the Violence Against Women Act that allowed victims of sexual violence to sue their attackers in federal court.

In recent years, however, the state's rights trend started by those decisions has stalled.

In June, the court ruled 6-3 that the U.S. Justice Department had the authority to prosecute two seriously ill women in California who used marijuana as a painkiller. O'Connor accused the majority, which included Scalia and Kennedy, of "rewriting" the Constitution's Commerce Clause, which gives the national legislature authority only over interstate commerce.

One of the few judicial opinions by Roberts that has inspired controversy is a dissent he wrote when the D.C. Circuit dealt with a real-estate developer's challenge to the constitutionality of the Endangered Species Act as it applied to an animal that lived only in one state. Roberts complained that "the panel's approach in this case leads to the result that regulating the taking of a hapless toad that, for reasons of its own, lives its entire life in California, constitutes regulating 'Commerce ... among the several States."

Next term the Supreme Court will decide whether the Commerce Clause empowers the federal government to prevent physicians in Oregon from dispensing drugs to terminally ill people who choose to end their lives. Physician-assisted suicide is legal in Oregon, but the Justice Department convinced the 9th U.S. Circuit that the federal government had the power under the Commerce Clause to regulate prescription drugs.

A Roberts vote on this case would test the assertion by the liberal Alliance for Justice that he has a "crabbed view of congressional power under the Commerce Clause" that "might threaten to undermine a wide swath of federal protections, including many environmental, civil rights, workplace and criminal laws."

Another case next term that raises federalism questions concerns an attempt to collect $400,000 owed to a bankrupt bookstore chain by four state-funded colleges in Virginia.

The 6th U.S. Circuit Court of Appeals ruled for the bookstore, holding that Article I of the Constitution gives the federal government jurisdiction over bankruptcy issues and thus created an exception to the immunity granted to states by the 11th Amendment.

Back in 1996, O'Connor joined the four other members of the "Federalism Five" in a decision striking down a federal law allowing Indian tribes to sue state governments in federal court if the states wouldn't negotiate with the tribes over gambling rights. If Roberts takes the same view of the 11th Amendment, the court likely would rule for Virginia in the bankruptcy case.

National security
Roberts has drawn criticism from civil libertarians for joining a recent opinion in which the D.C. Circuit upheld the Bush administration's procedures for military tribunals to try foreign detainees at the Guantanamo Bay Naval Base in Cuba.

However, the first test of Roberts' attitude toward presidential authority would come in a very different context. On Nov. 29 the justices will hear arguments in a case challenging a law that requires law schools that receive federal funds to allow military recruiters on campus.

Under a nondiscrimination policy adopted by the American Association of Law Schools, virtually every law school in the nation requires recruiters to sign a statement affirming that they do not discriminate on the basis of sexual orientation. After law schools turned away recruiters because of the armed services' policies against open homosexuality, Congress passed the Solomon amendment in 1994 ordering law schools that receive federal funds to welcome military recruiters.

The 3rd U.S. Circuit Court of Appeals in Philadelphia ruled 2-1 that the Solomon amendment violated the First Amendment. In asking the Supreme Court to review the ruling, the Bush administration has made two arguments: that the Solomon amendment does not interfere with free speech because the schools are free to decline federal funding, and that access for military recruiters is important "in the global war on terrorism."