An appropriations bill signed by President Bush last week allows the controversial National Applications Office to begin operating a stringently limited version of a program that would turn military spy satellites on the US, sharing imagery with other federal, state, and local government agencies. The government's own watchdog agency, the Government Accountability Office, has warned in an unpublished report that the more expansive program in the offing lacks adequate safeguards to protect privacy and civil liberties.

For now, the law restricts the NAO to "activities substantially similar" to those carried out by the Civil Applications Committee, an interagency coordinating body formed in 1976 to give civilian agencies access to military satellites for scientific and disaster preparedness purposes, such as "monitoring volcanic activity, environmental and geological changes, hurricanes, and floods." But as a draft charter for the Office makes clear, officials at the Department of Homeland Security hope to branch out from these traditional applications, providing assistance and information to domestic law enforcement agencies.

That doesn't sit well with some members of Congess, who in a sharply worded letter earlier this year expressed concerns that the NAO "raises major issues under the Posse Comitatus Act" barring the military from performing law enforcement duties, and worried the program could be used to "gather domestic intelligence outside the rigorous protections of the law—and, ultimately, to share this intelligence with local law enforcement outside of constitutional parameters."

And as the Wall Street Journal reported last week, the Government Accountability Office appears to share those concerns. In an unpublished analysis—a public version of which may be released in coming weeks—the GAO found that there did not seem to be adequate "assurance that NAO operations will comply with applicable laws and privacy and civil liberties standards," nor sufficient checks and oversight procedures to prevent the misuse of satellite imagery.

The existence of the NAO was first publicly disclosed in press reports last summer, several months after its creation at the behest of the Director of National Intelligence. Following hearings held by the House Committee on Homeland Security, Congress blocked funding for the NAO, pressing DHS for more information about the legal basis for the progam—as well as the privacy safeguard to be put in place. The current appropriations bill permits the NAO to be funded only for the purpose of carrying out the old Civil Applications Committee's functions, pending a certification by the Secretary of Homeland Security that the Office's compliance with the law has been vetted, and provision to the Appropriations Committee of details of how funds will be spent. The bill also directs the Inspector General to provide regular reports—somewhat oddly, to the Appropriations Committee—on the data collected by NAO.

Among the questions raised about the proposed program is whether it runs afoul of the Reconstruction Era statute that makes it a crime to use the armed forces to "execute the laws" within US borders. Tim Sparapani, senior legislative counsel with the American Civil Liberties Union, believes the new initiative to be "a prima facie violation of the Posse Comitatus Act—this is about using a military asset to do domestic law enforcement." If law enforcement or immigration agencies need spy satellites, he argues, they should ask Congress to buy them some, rather than using the powerful eyes in the sky operated by the National Reconaissance Office for foreign-intelligence agencies not bound by domestic privacy constraints. "The military should never be used against the citizenry," he argues. "Even if we're talking about shooting pictures of people instead of shooting people, the principle remains the same."

But Gene Healy, an attorney and scholar at the libertarian Cato Institute, is not so sure. At least since the 70s, says Healy, courts have tended to read the prohibition on using the military to "execute the laws" only as a barrier to "hands-on policing," such as conducting arrests or doing crowd control. That means sending soldiers to physically search a criminal suspects home is out, but loaning expertise or equipment and sharing information may be allowed. During the 2002 hunt for the "DC sniper," he notes, Army aircraft were used in the effort to hunt down the serial killer. "That doesn't mean it's a good policy," says Healy, "I can think of a lot of reasons it's a really bad idea to let soldiers train narcotics officers too, but that doesn't mean either is illegal under the current statute."

And what of Fourth Amendment concerns? Here, Sparapani says, the program enters "uncharted waters." In a pair of 1986 decisions, the Supreme Court ruled that aerial observation by surveillance planes did not count as a Fourth Amendment "search." If you grew your marijuana out in the open, the justices essentially concluded, you could not claim a "reasonable expectation of privacy" even if the crop wasn't visible from the ground. But the court left open the question of whether the same logic would apply in the case of technology more esoteric than an airplane. And in 2001, the court concluded that a search warrant was needed to use infrared scanners to detect the heat signature from an indoor dope-growing operation.

Presumably intelligence satellites have a range of sophisticated scanning equipment that would fall under the latter rule. But even in the case of ordinary image capturing, the high degree of precision of the satellite cameras—by some accounts good enough to read a page of text in a subject's hand—may make spying from space qualitatively different from a plane flyover.

Whatever the courts decide, Sparapani argues that Congress should press DHS to be more forthcoming about how it plans to use the orbiting eyes. "Given this administration," he says, "'trust us' just doesn't work anymore."