From U.S. News (H/T Hugh Hewitt):

In search of a terrorist nuclear bomb, the federal government since 9/11 has run a far-reaching, top secret program to monitor radiation levels at over a hundred Muslim sites in the Washington, D.C., area, including mosques, homes, businesses, and warehouses, plus similar sites in at least five other cities, U.S. News has learned. In numerous cases, the monitoring required investigators to go on to the property under surveillance, although no search warrants or court orders were ever obtained, according to those with knowledge of the program. Some participants were threatened with loss of their jobs when they questioned the legality of the operation, according to these accounts.

More:

Federal officials familiar with the program maintain that warrants are unneeded for the kind of radiation sampling the operation entails, but some legal scholars disagree. News of the program comes in the wake of revelations last week that, after 9/11, the Bush White House approved electronic surveillance of U.S. targets by the National Security Agency without court orders. These and other developments suggest that the federal government's domestic spying programs since 9/11 have been far broader than previously thought.

On the question of whether warrants were needed:

To ensure accurate readings, in up to 15 percent of the cases the monitoring needed to take place on private property, sources say, such as on mosque parking lots and private driveways. Government officials familiar with the program insist it is legal; warrants are unneeded for monitoring from public property, they say, as well as from publicly accessible driveways and parking lots. "If a delivery man can access it, so can we," says one.

Georgetown University Professor David Cole, a constitutional law expert, disagrees. Surveillance of public spaces such as mosques or public businesses might well be allowable without a court order, he argues, but not private offices or homes: "They don't need a warrant to drive onto the property -- the issue isn't where they are, but whether they're using a tactic to intrude on privacy. It seems to me that they are, and that they would need a warrant or probable cause."

Cole points to a 2001 Supreme Court decision, U.S. vs. Kyllo, which looked at police use -- without a search warrant -- of thermal imaging technology to search for marijuana-growing lamps in a home. The court, in a ruling written by Justice Antonin Scalia, ruled that authorities did in fact need a warrant -- that the heat sensors violated the Fourth Amendment's clause against unreasonable search and seizure. But officials familiar with the FBI/NEST program say the radiation sensors are different and are only sampling the surrounding air. "This kind of program only detects particles in the air, it's non directional," says one knowledgeable official. "It's not a whole lot different from smelling marijuana."

It's really no surprise that the government is monitoring for radiation, as the possibility of a nuclear "dirty bomb," or even a fully operational suitcase nuclear device with catastrophic destructive power, was a major concert in the days and months after 9/11.

However, this question of whether authorities encroached upon private property without warrants, when warrants may indeed have been required, needs to be examined further.

What also needs to be examined is who is leaking this stuff? The information is going right into the hands of our enemies, and whoever or whomever is leaking it needs to be discovered and prosecuted to the full extent of the law.