Justice Sandra Day O'Connor (search) extolled Wednesday the growing role of international law in U.S. courts, saying judges would be negligent if they disregarded its importance in a post-Sept. 11 world of heightened tensions.

In a 15-minute speech at Georgetown law school, O'Connor made no mention of the health of Chief Justice William H. Rehnquist (search), 80, who was hospitalized this week for thyroid cancer and is expected to return to work Monday. There also was no additional details from a court spokeswoman on his condition Wednesday.

O'Connor said the Supreme Court (search) is increasingly taking cases that demand a better understanding of foreign legal systems. A recent example was last term's terror cases involving the U.S. detention of foreign-born detainees at Guantanamo Bay, Cuba, she said.

"International law is no longer a specialty. ...It is vital if judges are to faithfully discharge their duties," O'Connor told attendees at a ceremony dedicating Georgetown's new international law center.

"Since Sept. 11, 2001, we're reminded some nations don't have the rule of law or (know) that it's the key to liberty," she said.

Later this term, the Supreme Court will decide the constitutionality of executing juvenile killers. The case has attracted wide interest overseas, with many foreign nations filing briefs pointing to international human rights norms as a justification for outlawing the practice.

O'Connor, who is expected to be a pivotal vote, didn't mention the case but said recognizing international law could foster more civilized societies in the United States and abroad. "International law is a help in our search for a more peaceful world," she said.

The 74-year-old who battled a 1988 bout with breast cancer also did not discuss any potential retirements by her colleagues, a topic of much discussion after the surprise announcement Monday of Rehnquist's hospitalization.

Instead, O'Connor said she looked forward to working with many Georgetown students and faculty who might eventually become Supreme Court clerks or argue cases before the justices.

"I look forward to many contacts with you in the years ahead. You will be very good neighbors indeed," she said.