By Alister Doyle Environment Correspondent
BONN, Germany (Reuters) - Climate activists will argue in an Oslo court this week that Norway's plans for Arctic oil exploration are unconstitutional, in an emerging branch of law where plaintiffs are trying to enlist a nation's founding principles to limit warming.
The cases, including one in the United States where a group of young people are arguing that global warming threatens their Fifth Amendment right to life, liberty and property, are widening the scope of environmental litigation.
Some legal scholars say it is a stretch to invoke the Constitution rather than focus on taxes and regulations to control greenhouse gases. Governments including the U.S. Trump administration and Norway are dismissive.
Still, some cases have succeeded, such as a 2015 case that told the Dutch government to cut greenhouse emissions.
And worldwide, 90 national constitutions have some sort of provisions guaranteeing environmental protection. Article 112 of Norway's constitution speaks of safeguarding a healthy environment for future generations.
"We want the court to recognize that climate change is not some side issue but a fundamental core issue," said Jennifer Morgan, executive director of Greenpeace whose lawyers will go to court in Oslo from Tuesday.
"The constitution represents those basic rights," she told Reuters in Bonn, Germany, where almost 200 nations are working on ways to bolster the 2015 Paris climate agreement after President Donald Trump decided in June to pull out.
The Norwegian case, brought by Greenpeace and the Nature and Youth group, argues that a 2015 oil licensing round in the Arctic violates the constitution because Norway has agreed to the Paris accord's goals to end the fossil fuel era this century.
Norway's attorney general argues that the oil licenses, awarded to Statoil, Chevron, Lukoil, ConocoPhillips and others, have no link to the Constitution. Norway's environmental laws are among the toughest in the world.
The plaintiffs' case is based on "a distinctly broad, political, and expanded interpretation of the Constitution's article 112," the Attorney General's office said in court documents.
Environmentalists say the case is far more than a stunt. Losing could mean having to pay the state's legal fees, meaning a total bill exceeding $500,000.
Worldwide, there are almost 900 lawsuits related to climate change in 25 nations, a U.N. study said in March.
Among them, a Peruvian farmer launched an appeal in Germany on Monday, arguing that greenhouse gas emissions by energy utility RWE are partly to the blame for melting an Andean glacier that is threatening to cause floods.
A lower court last year rejected his call for compensation.
Cases have risen since the Paris Agreement in 2015. Adding relevance, researchers increasingly say that greenhouse gas emissions have raised the risks of individual extreme events, from heat waves in Europe to downpours in India.
That could herald more claims.
"Flooding in New York after superstorm Sandy (in 2012) would have been less severe without a rise in sea levels," said Michiel Shaeffer, science director of research group Climate Analytics.
Still, courts are a "blunt instrument" to try to force change on climate policies, said Oonagh Fitzgerald, a legal expert at the Centre for International Governance Innovation in Canada.
"And for a lot of people it seems far-fetched" to link climate change with fundamental rights, she said.
Kiran Oommen, aged 20, is among 21 young plaintiffs in the U.S. case accusing the government of allowing emissions of greenhouse gases to rise even when it knew they could disrupt the climate.
He said that rising seas threatened his uncle and aunt's home in Florida and his brother developed allergies because of high pollen levels in Oregon linked to warmer temperatures.
The court case is due to start on Feb. 5, after judges rejected attempts by both the Obama and Trump U.S. administrations to have it dismissed.
And the Dutch government is appealing against a 2015 court ruling that ordered it to slash emissions by 25 percent from 1990 levels by 2020, more deeply than planned, to care for its citizens.
"The relevant question in all these cases is 'is there an obligation on a state that goes further than what the laws of parliament say?'" said Dennis van Berkel, legal counsel of the Urgenda Foundation which represented 900 co-plaintiffs.
He said legal arguments in the Dutch case were based mainly on the civil code, backed up by the Constitution, which obliges authorities "to keep the country habitable and to protect and improve the environment."
(With extra reporting by Gwladys Fouche and Terje Solsvik in Oslo; Editing by Andrew Heavens and Toby Chopra)