Without comment, the justices put on hold a judge's ruling that it is unconstitutional to impose a blanket policy closing all detention or deportation hearings that the government calls special-interest cases.
The administration had argued that national security would be threatened if reporters and others were allowed to attend the hearings. The intervention was the first by the court in a dispute arising from the government's response to the attacks.
Civil rights and media organizations are seeking information on an unknown number of foreign nationals held by the Immigration and Naturalization Service since Sept. 11.
"More people will be tried in secret, and that's unfortunate," said Lee Gelernt, an American Civil Liberties Union attorney specializing in immigrant rights. "They're appearing all by themselves in front of a judge, facing a trained INS prosecutor in secret. There's no public scrutiny of the process."
U.S. District Judge John Bissell in Newark, N.J., ruled last month that the government could close hearings on a case-by-case basis.
"If these proceedings are opened to the public during the critical phase of the urgent threat to national security, terrorist organizations will have direct access to information about the government's ongoing investigation," Bush's top Supreme Court lawyer, Theodore Olson, wrote in a court filing.
Olson said the hearings could reveal identities of foreign detainees, evidence of their links to terrorism and clues to how much the government knows about wider terrorist operations.
"This is clearly a victory for the administration," said CBSNews.com Legal Analyst Andrew Cohen. "The Justice Department had asked the Supreme Court to stay this order opening up the hearings on national security grounds, and at least for the time being, the Supreme Court is willing to give the administration the benefit of the doubt."
The stay will give the 3rd U.S. Circuit Court of Appeals time to review Bissell's May 29 ruling. The government has asked the court in Philadelphia to overturn the decision.
The appeals court agreed to quickly hear arguments in the case, but refused to stop open hearings in the meantime.
The closed hearings were challenged by the ACLU and the New York-based Center For Constitutional Rights on behalf of the New Jersey Law Journal, a weekly publication, and North Jersey Media Group, publisher of the Herald News of West Paterson, a daily newspaper.
More than 100 foreign nationals picked up after Sept. 11 were still in custody as of late May, down from about 700, the Justice Department has said.
The government has provided no updated figure, nor information about the charges detainees face. An unknown number have apparently pleaded guilty to immigration charges and have been deported.
The case is Ashcroft v. North Jersey Media Group, A-991.