John Wild (johnwild.info)

The Transportation Security Agency violated federal law when installing controversial full-body scanners in U.S. airports without following proper procedures, a federal appeals court ruled today.

The D.C. Circuit Court of Appeals in Washington, D.C., rejected arguments from the Obama administration that the TSA was exempt from laws requiring federal agencies to first notify the public and seek comments.

"It is clear that by producing an image of the unclothed passenger, (a full-body) scanner intrudes upon his or her personal privacy in a way a magnetometer does not," wrote Judge Douglas Ginsburg for the three-judge panel.

Ginsburg said he would not order TSA to immediately halt the full-body screening--which resulted in a near-revolt by air travelers last fall--but instead instructed "the agency promptly to proceed in a manner consistent with this opinion."

The Electronic Privacy Information Center, a Washington, D.C.-based advocacy group, filed the lawsuit in July 2010 asking for an immediate injunction pulling the plug on TSA's body scanning program.

EPIC executive director Marc Rotenberg said today: "The TSA is now subject to the same rules as other government agencies that help ensure transparency and accountability. Many Americans object to the airport body scanner program. Now they will have an opportunity to express their views..."

The appeals court's ruling today sided with the TSA in some areas, however. EPIC had claimed that the scanners violated the Fourth Amendment's prohibition on "unreasonable" searches.

On the contrary, the court said, the need to search passengers is "particularly acute" and air travelers have the option to choose a police-style patdown instead: "Considering the measures taken by the TSA to safeguard personal privacy, we hold (that full-body) screening does not violate the Fourth Amendment."

Last updated at 4:19 p.m. PT

Clarification: The headline on this story was changed for clarity. TSA must halt body scanners unless it can demonstrate through the formal regulatory process that body scans are necessary.