The Department of Justice asked a federal court Thursday to dismiss a pair of lawsuits targeting a slew of oil companies for allegedly contributing to man-made global warming.

Oakland and San Francisco sued five energy companies in March for engaging in a nearly decades-long misinformation campaign about the science of climate change. Both cities want Chevron and others to fork over billions to cover the cost of sea walls to combat rising sea levels.

“Balancing the nation’s energy needs and economic interests against the risks posed by climate change should be left to the political branches of the federal government in the first instance,” Acting Assistant Attorney General Jeffrey Wood wrote in an amicus brief. Executive and legislative branches are better suited to address effects from climate change, the DOJ claims.

The cases should be dismissed because the Clean Air Act prevents cities from taking action on such matters, according to the DOJ. Allowing the cases to continue violate the separation of powers principle in the U.S. Constitution, the department also claims.

DOJ also gives the cities and activists credit for their novel approach to tackling global warming. The production of fossil fuels, rather than fuel emission combustion, is the principle cause for climate change, they essentially argue.

San Francisco and Oakland are relying on a similar theory of liability conservationists used in a 2011 case arguing five electric utilities in Tennessee were the largest sources of greenhouse gases, DOJ claims. The Supreme Court eventually dismissed the case, claiming the EPA’s Clean Air Act holds jurisdiction over such matters.

The court would need to determine what portion of the fossil fuel produced was used as combustible fuel and what percentage of that fuel contributed to total greenhouse gas emissions across the globe, the DOJ added in its brief.

San Francisco and Oakland are two of eight California cities suing fossil fuel companies for damages allegedly wrought by man-made global warming. New York City; Boulder, Colo.; and two Colorado counties are also suing energy companies for “knowingly” causing global warming.

The suits, largely handld by trial lawyers on a contingency fee basis, rest on public nuisance and trespassing claims, which have sometimes been applied to pollution issues. But legal efforts have questioned the logic of applying nuisance claims to a global phenomenon, like global warming. (RELATED: High-Powered NYU Legal Prof Says California-Climate Lawsuits Don’t Stand A Chance)

Lawsuits against fossil fuels companies are also problematic for an obvious reason — their customers are the major source of emissions, not the companies themselves.

“Indeed, these public nuisance lawsuits are especially dubious, given that the oil companies did not by their sales emit any carbon dioxide into the atmosphere,” New York University Law Professor Richard Epstein noted in a January 25 article. (RELATED: Watchdog Group Launches Website Exposing Intimate Aspects Of Enviro-Led Climate Litigation)

The county housing Seattle, Wash., also filed a lawsuit Thursday targeting Exxon, Chevron, Conoco Phillips and several other oil companies for contributing to the effects of climate change.

The suit, which was brought by Seattle-based law firm Hagens Berman Sobol Shapiro, seeks to create an abatement fund addressing changes to infrastructure, like bridge maintenance, salmon recovery and public health

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