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A federal judge has ordered the Army to track down soldiers who were subjected to secret medical experiments during the Cold War and warn them of any newly discovered health hazards they could face.

In a ruling (PDF) entered Thursday in U.S. District Court in Oakland, Calif., Judge Claudia Wilken lifted a stay she had briefly imposed on her earlier ruling that the Army must keep soldiers who took part in the tests up to date. The government wanted the ruling to remain shelved while it pursued appeals.

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The experiments, many of them conducted as part of a program called Operation Paperclip, tested hundreds of chemical and biological agents — including LSD, the nerve gas sarin, mustard gas and amphetamines — on soldiers beginning in the early 1950s.

President Richard Nixon ended the program in 1969, and all chemical testing on humans is believed to have ended in 1976.

The issue isn't that the approximately 7,800 soldiers didn't know that they were being used in the experiments — all of them signed consent agreements, lawyers representing them in the class-action suit acknowledge. Instead, they argue, the Army abandoned the soldiers once the terms of their consent expired, generally after five years.

But Wilken ruled in November (PDF) that the Army has an obligation to continue tracking the test subjects and to alert them to new information developed after 2006 about the effects of the agents they were given. The order she filed Thursday directs the Army to comply even though it's still appealing her decision.

Government lawyers had argued that the cost of implementing the order — which they estimated at $1.8 million a year — would constitute an "irreparable harm."

But Wilken wrote that that was an insignificant burden compared to the "irreversible health consequences" suffered by the soldiers.

The government also argued that courts have no jurisdiction to assess the medical judgments of military scientists and that there is no constitutional right to notice or health care. Wilken sided with the government on some claims, removing the CIA and Attorney General Eric Holder from the suit.