In 2011, Canada’s largest pension fund plowed about $760 million into a state-controlled Norwegian pipeline network, citing the country’s transparent regulatory environment and expecting the project to deliver stable returns for a long time.

One risk the Canada Pension Plan Investment Board didn’t see coming was that the government of Norway, which prides itself on being one of the world’s safest corners for investors, would slash the rates the pipeline can charge for carrying natural gas.

The fund, along with another Canadian pension plan and some of the world’s largest institutional investors, is now suing the Norwegian government, whose action will cut the amount of revenue they are paid. The investors say they may only get half of the return they had expected, leading to multibillion-dollar losses. The plaintiffs haven’t said what damages they are seeking.

“Sophisticated, long-term infrastructure investors have seriously recalibrated their assessment of Norway,” said Mark Wiseman, chief executive of CPPIB, in a letter last year to the Norwegian finance ministry.

With yields on debt securities at rock-bottom levels, the lure of steady, long-term returns is drawing many big investors to pipelines, ports and other infrastructure projects. But bankers and lawyers in the sector say the Norwegian case has some investors reassessing the political risk of this kind of investment in Europe, where governments, especially of Nordic countries, have been seen as reliable partners.