Public Citizen and San Luis Obispo Mothers for Peace, a community-based California organization concerned with nuclear safety issues, challenged a Nuclear Regulatory Commission rule defining the design basis threat - that is, the threat of terrorism against which nuclear plants must be capable of defending themselves. The NRCs rulemaking proceeding arose out of an earlier lawsuit filed by Public Citizen and Mothers for Peace, which pointed out that the NRC had unlawfully revised the rule without proper rulemaking procedures. That lawsuit was mooted when the NRC agreed to engage in rulemaking, but the result of the rulemaking was an inadequate rule that, among other things, does not require nuclear plants to defend against 9/11-style air attacks. Because of the rules deficiencies, Public Citizen and Mothers for Peace sought review of the rule in the United States Court of Appeals for the Ninth Circuit, where the case was been consolidated with a similar challenge brought by the Attorney General of the State of New York. On July 24, 2009, the Ninth Circuit denied the petition.