In Pacific Merchant Shipping Association v Cackette, 9th Cir, No 07-16695, 23.10.07 a federal appeals court lifted an injunction blocking California from requiring marine vessels to use cleaner burning fuels to power auxiliary engines, pending the appeal of a trial court decision that concluded the Clean Air Act pre-empted the requirement.

It therefore permits the California Air Resources Board to enforce State rules reducing diesel emissions from domestic and foreign-flagged ships sailing within 24 nautical miles of the California coast. Stricter emissions standards began in January 2007 with tighter standards coming into effect in 2010. The merits of the legal issues are still before the Ninth Circuit Court of Appeals, which has said it will expedite appeals concerning these rules