"It is a big deal for the court to do that. It is the first time it has happened in the US," said Margaret Mellon, director of the Union of Concerned Scientists Food and Environment Program, which is not a party to the case.

There have been concerns for years about the USDA's lack of proper oversight. Indeed, other recent court rulings have leveled criticism against US government oversight of biotech crops.

"There are some serious problems there," said Mellon. "They need to be fixed."

USDA officials would not comment Tuesday, a day after US District Court Judge Charles Breyer of the Northern District of California issued an order on Monday that vacated USDA approval of Monsanto Co.'s "Roundup Ready" alfalfa.

The crop, genetically altered to withstand treatments of Monsanto's Roundup herbicide, was approved in 2005. But Judge Breyer immediately halted any more seed sales and ordered that any planting must cease after March 30 after he determined that the USDA violated the law in allowing unrestricted commercial planting of the crop.

The judge said the USDA should have prepared an environmental impact statement before deregulating the Roundup Ready alfalfa. Such a statement is designed to explore negative consequences that might result from a release.

In the case of biotech alfalfa, a perennial livestock feed crop, several farm, environmental and consumer activists groups said there were many potential problems, including contamination of organic and conventional alfalfa supplies with the biotech version.

Other crops, including most notably corn and rice, have already been contaminated with biotech varieties, forcing in some situations costly recalls and lost export sales.

"I challenged them over and over to give us any scientific evidence that they can control the gene flow from these crops. So far they haven't been able to do that," said Andrew Kimbrell, executive director of The Center for Food Safety, which led the lawsuit against the US Agriculture Department.

"This technology was put out into the environment without any idea of how to control it," he said. "Now the agency for the first time will have to come up with some sort of answers as to how you can control this and be accountable for it."

Like USDA, Monsanto officials also declined to discuss the potential ramifications of the ruling Tuesday, but company spokeswoman Lori Fisher said Monsanto was informing Roundup Ready alfalfa seed dealers of the court order and outlining actions they must take.

"Basically, this communication informs dealers to stop sales of Roundup Ready alfalfa under court order, to secure Roundup Ready alfalfa seed not sold in inventory and to expect further instructions as the situation develops," Fisher said.

Over the last decade, the USDA has approved applications for more than 70 genetically modified organism (GMO) crop lines, many of which have been embraced by farmers because they are easier and/or more profitable to grow.

Sharon Bomer, a vice president at the Biotechnology Industry Organization (BIO), said her group, which represents the interests of biotech companies, including Monsanto, said that the safety of alfalfa and other commercialized biotech crops was not an issue. And she said the court ruling on alfalfa appeared limited.

"We think this deals with only one situation," she said.

Still, the oversight, primarily handled by the USDA's Animal Health and Plant Health Inspection Service, has been repeatedly criticized as lacking. An Office of Inspector General audit of APHIS' and its biotechnology regulatory services unit found numerous holes in oversight efforts in a report issued in December 2005.

The government is currently reviewing and rewriting the regulations for field testing and for deregulation of genetically modified crops with a final report on the overhaul due out in the next few months.

In the meantime, Kimbrell said he was dismayed that the USDA appears to remain more focused on supporting Monsanto's commercial needs than on protecting the interests of others in agriculture.