The U.S. Constitution does not outlaw sex discrimination or discrimination based on sexual orientation, Supreme Court Justice Antonin Scalia told a law school audience in San Francisco on Friday.

"If the current society wants to outlaw discrimination by sex, you have legislatures," Scalia said during a 90-minute question-and-answer session with a professor at UC Hastings College of the Law. He said the same was true of discrimination against gays and lesbians.

The 74-year-old justice, leader of the court's conservative wing, is also its most outspoken advocate of "originalism," the doctrine that the Constitution should be interpreted according to the original meaning of those who drafted it.

The court has ruled since the early 1970s that the 14th Amendment's guarantee of equal protection of the laws applies to sex discrimination, requiring a strong justification for any law that treated the genders differently. That interpretation, Scalia declared Friday, was not intended by the authors of the amendment that was ratified in 1868 in the aftermath of the Civil War.

"Nobody thought it was directed against sex discrimination," he said. Although gender bias "shouldn't exist," he said, the idea that it is constitutionally forbidden is "a modern invention."

The court has not applied the same exacting standard to discrimination based on sexual orientation, an issue it could reach in several cases now in lower courts, including the dispute over California's ban on same-sex marriage.

But when the justices overturned laws against gay sex in 2003 as a violation of personal autonomy and due process, Scalia dissented vehemently. He compared the anti-sodomy laws to statutes against incest and bestiality and said many Americans view bans on homosexual conduct as protections for themselves and their families against "a lifestyle that they believe to be immoral and destructive."

Scalia said Friday he's not a purist and is generally willing to accept long-standing court precedents that contradict his views. One exception, he said, is abortion, in which he continues to advocate overturning the 1973 Roe vs. Wade decision and later rulings that have narrowed but not eliminated the constitutional right to terminate one's pregnancy.

He derided the court's 1992 Casey decision, which allowed states to restrict abortion as long as they did not place an "undue burden" on women's access to the procedure.

Having to decide whether a new staffing requirement for abortion facilities, for example, imposes an undue burden "puts me in the position of being a legislator rather than a judge," he said. "That's not law, and I won't do it."

He also described the legal underpinnings of the court's 1965 ruling declaring a constitutional right of privacy - the basis for Roe vs. Wade - as a "total absurdity."

Scalia is the longest-serving justice on the current court. He spoke to an auditorium filled with law students on the 24th anniversary of his unanimous Senate confirmation, after his appointment by President Ronald Reagan.

He said most of his views haven't changed since then, but one exception is the idea of allowing cameras in the court, which he supported when he was appointed. The issue resurfaced in January when a 5-4 majority, including Scalia, vetoed a federal judge's plan to allow closed-circuit televising of the same-sex-marriage trial in San Francisco.

"If I really thought it would educate the American people, I would remain in favor of it," he told the students. But instead of educational gavel-to-gavel coverage, he said, most people would see 30-second snippets on the nightly news that would "distort the public perception of the court."