Five cities and counties in California that are suing fossil fuel companies for damages triggered by climate change are now at the center of a legal paradox created by conflicting decisions from two federal court judges reviewing nearly identical claims.

The judicial collision course was set Friday when a federal judge in San Francisco ruled that climate change lawsuits by two counties and one city were best adjudicated in California state courts. The ruling came less than a month after another federal court judge ruled that a similar climate case, brought by the cities of San Francisco and Oakland, should be tried in federal court.

The contradictory rulings by the judges—both Democratic appointees who serve in the same San Francisco courthouse just two floors apart—were handed down in lawsuits targeting oil and gas companies, including Exxon, Chevron, BP, ConocoPhilips and Shell, for damages associated with climate change.

Both lawsuits are anchored in California public nuisance law and argue that the oil and gas companies have created a public nuisance because the heat-trapping greenhouse gases generated by burning fossil fuels are responsible for sea level rise that threatens their communities. But the oil and gas companies want the cases argued in federal court, where they contend they have a more level playing field.

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Hearing the cases in state court gives the cities and counties an edge because California has a stronger public nuisance law than the federal court system, legal experts say.

California laws come down heavily in favor of plaintiffs filing civil liability cases, said Pat Parenteau, a professor of environmental law at the Vermont Law School.

He cited a recent California case in which three paint manufacturers were ordered to pay more than $1 billion to California counties and cities for their alleged contributions to a "public nuisance" caused by the presence of lead paint in old homes.

It's that kind of precedent that bodes well legally for the cities and counties in the climate cases, and illuminates the urgency of the oil and gas companies to get the cases out of California state courts.

"This is the best possible venue you could hope for to seek damages for sea level rise," Parenteau said. "You would want to get this kind of case before a local judge and jury in California."

The cities and counties are seeking billions of dollars from the companies to cover the costs of past and future damage incurred because of rising oceans that include building seawalls and rebuilding damaged infrastructure.

Chhabria: Why the Cases Belong in State Court

In Friday's ruling, U.S. District Court Judge Vincent Chhabria decided California state courts were the appropriate setting for the climate lawsuits brought by San Mateo and Marin counties, near San Francisco; and the City of Imperial Beach, a small city south of San Diego.

The oil and gas companies maintained the lawsuits raised issues more closely related to federal laws than state laws, primarily that the federal Clean Air Act should be the controlling law when addressing issues associated with emissions.

But Chhabria was not moved by those arguments.

"To justify removal from state court to federal court, a defendant must be able to show that the case being removed fits within one of a small handful of small boxes," the judge wrote in his ruling. "Because these lawsuits do not fit within any of those boxes, they were properly filed in state court and improperly removed to federal court"

Chhabria, who appointed to the bench in 2014 by President Barack Obama, acknowledged that his ruling disagreed with the earlier ruling by U.S. District Judge William Alsup that kept the San Francisco and Oakland lawsuits in federal court.

Chhabria stayed his order for six weeks to give the oil and gas companies time to file an appeal.

Similar lawsuits filed by Santa Cruz County and the cities of Santa Cruz and Richmond also are pending a ruling by Chhabria over the appropriate legal venue.

Alsup: Why Federal Court's Best for Cities' Suits

When Alsup sided with the fossil fuel companies last month and ruled that the San Francisco and Oakland cases would be heard in federal court, he also ordered a five-hour climate science tutorial scheduled for March 21, during which lawyers for both sides will discuss the current state of climate science.

Alsup, who was appointed to the bench by President Bill Clinton in 1999, rejected the cities' argument that their claims arise under California public nuisance law, finding instead that federal common law applies in global warming cases.

"Taking the complaints at face value, the scope of the worldwide predicament demands the most comprehensive view available, which in our American court system means our federal courts and our federal common law," Alsup wrote in his Feb. 27 decision.

The judge acknowledged the peril of climate change and the role burning of fossil fuels plays in global warming, singling out wildfires, melting polar ice caps and sea level rise as consequences.

Yet, he said he worried that addressing these issues in state courts could lead to piecemeal resolutions.

"A patchwork of 50 different answers to the same fundamental global issue would be unworkable," Alsup wrote. "This is not to say that the ultimate answer under our federal common law will favor judicial relief. But it is to say that the extent of any judicial relief should be uniform across our nation."

There's no apparent legal reason the conflict between the rulings will have to be resolved.

"For the time being, it appears the two sets of cases will proceed on different tracks," said Vic Sher, one of the lead attorneys for the law firm of Sher Edling representing Marin and San Mateo counties and the City of Imperial Beach. "Both sets of cases could succeed—or fail—for many different reasons."

Read more about Judge Alsup's questions for the climate science tutorial: 8 Answers to the Judge's Climate Change Questions in Cities vs. Fossil Fuels Case