* Gassled partners have six weeks to decide on appeal
* Government satisfied with decision -oil ministry (Adds detail from ruling, reaction, firms' bond ratings)
By Stine Jacobsen and Gwladys Fouche
OSLO, Sept 25 (Reuters) - An Oslo court ruled on Friday infavour of Norway in a lawsuit involving a group of internationalinvestors who argued that Norway's decision to cut natural gaspipeline tariffs would cost them 15 billion crowns ($1.8billion) in lost earnings by 2028.
Challenging Norway's reputation as a predictable place to dobusiness, four firms owned by funds including Allianz,UBS, the Abu Dhabi Investment Authority and the CanadaPension Plan Investment Board, argued that Norway illegally cutfees on the 8,000-km (5,000-mile) Gassled gas pipeline network.
The four firms, which hold a combined 45 percent stake inGassled, said they would consider whether to appeal thedecision.
"All four plaintiffs will now evaluate this in detail andassess the next step within the next six weeks, which is thedeadline," Kurt Georgsen, CEO of Gassled partner Silex Gas, toldReuters.
The stakes were bought in 2010 and 2011 from ExxonMobil, Total, Statoil and Royal Dutch Shell.
The Oil and Energy Ministry had not provided fullinformation to the buyers and sellers regarding how the tariffscould be changed, the court said, but added that the ministry'sofficials themselves at the time had been unaware of how easilythis could be done.
"The ministry is to blame for this, but following an overallassessment the court concludes that the actions of theministry's leadership can't be regarded as qualifying negligence- which according to the law is a condition for triggeringliability," said the ruling.
The losing party in a lawsuit in Norway will most often betold to pay the winner's legal fees, but in the case of theGassled lawsuit, the government was partly to blame for the factthat it had gone to trial, the court said.
"Therefore, the parties shall pay their own legal costs," itadded.
The oil and energy ministry said in a statement that it was"satisfied" with the verdict.
The firms, many of which bought into Gassled in 2011 througha 17 billion crown deal for state-controlled Statoil's 24 percent stake, argued the tariff cut benefits gas producers,the very firms that sold them their stakes.
The state refuted the claim, arguing that returns were aboveagreed levels and fees were so high that they discouraged newoffshore investment.
It said most profit from oil and gas should be derived fromthe fields, not from the infrastructure, and that pipelinetariffs needed to be cut from October 2016 because the predictedreturns had been achieved.
One of the investors, Njord Gas Infrastructure, owned by UBSand France's Caisse des Depots, had its bond rating lowered in2013 to junk status from investment grade as a result of thechange in tariff. It is currently rated BB by Standard & Poor's.
Solveig Gas Norway, owned by the Abu Dhabi InvestmentAuthority, Allianz and the Canada Pension Plan Investment Board,also saw a multi-level downgrade of its bonds in 2013, andcurrently has a Baa2 rating by Moody's. (Additional reporting by Terje Solsvik, editing by David Evans)
