The US Supreme Court has dismissed a legal challenge to a domestic anti-terrorism eavesdropping programme.
President George W Bush authorised the monitoring, without a court order, of international phone calls and e-mails of US citizens after the 9/11 attacks.
The American Civil Liberties Union argued that Mr Bush did not have the constitutional authority to order the programme, which ended last year.
The Supreme Court gave no explanation for its ruling.
The domestic spying programme was denounced by Democrats and rights activists when it was disclosed in 2005.
A group of civil liberties activists, journalists, academics and lawyers challenged the spying programme in the courts, arguing it violated a 1978 rule prohibiting surveillance of American citizens on US soil without a warrant.
In July last year, an appeals court struck down a lower court's ruling that found the programme to be unconstitutional.
The appeals court, based in Cincinnati, dismissed the case because the plaintiffs had failed to show that their communications had been monitored.
But the Cincinnati judges did not rule on the legality or otherwise of the programme.
The president rejected claims that he broke the law by ordering surveillance without first securing warrants. He argued the eavesdropping programme was necessary and was targeted against al-Qaeda.
The Bush administration has so far refused to release documents about the programme that might reveal who was under surveillance.