The decision is largely regarded as a landmark victory for environmentalists.

The Obama administration has been issuing oil leases to companies across California without taking into account the possible risks that stem from fracking, thus breaking the law, a federal judge has ruled.

According to U.S. District Judge Paul Grewal, the U.S. Bureau of Land Management (BLM) issued the leases while completely disregarding environmental concerns and failing to ensure that drilling operations were safe. During the ruling in San Jose, Calif., Judge Grewal noted that the BLM had dismissed any possible fracking problems as "outside of its jurisdiction." Although the potential risk to the environment from fracking is unknown, it is not that speculative to be completely ignored, the judge said.

The decision came in response to a lawsuit filed by environmental groups and is largely regarded as a landmark victory for environmentalists, Reuters reported. However, Judge Grewal noted that his ruling only affected the legal aspects of lease distribution and did not look into the risks associated with fracking itself.

"Green" organizations have long been opposing fracking procedures, fearing that the practice could be harmful to natural habitats, land and waterways and also pointing to links between drilling operations and earthquakes across the United States. Environmentalists have been particularly concerned about fracking in California, since the state is already prone to drought and earthquakes. They worry that drilling could add further risk of water contamination and air pollution. Local residents have been reporting the appearance of cracks in their homes as a result of drilling. Last, but not least, environmentalists claim that fracking does not help the state of California to meet its targets for greenhouse gas emission reduction and address climate change issues.

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Brendan Cummings, a lawyer for the Center for Biological Diversity, which filed the lawsuit, told Reuters that this was the first federal court decision that explicitly states that federal agencies have to review all aspects of environmental impact before issuing oil and gas leases.

As an immediate effect of the ruling, drilling will be banned on the 2,500 acres of California land that were leased out for oil and gas development in 2011, affecting a total of four oil-drilling leases. The land is located on the Monterey Shale Formation, which holds one of the largest shale oil deposits in the United States. It is estimated that there are about 15 billion barrels of oil underneath the surface and that the Monterey Shale Formation accounts for 64 percent of the country's oil deposits.

As a result, California-based oil companies have had to put their work on hold and wait until a review has been conducted and their operations are deemed safe, when they hope they will be able to continue drilling. Tupper Hull, a spokesman for Western States Petroleum Association refinery group, commented that the ruling referred to the BLM process only and was not against fracking itself. Even though Hull told Reuters that the ruling was "a delay," he still hoped that leases would be allowed to go forward and production will take place.