A federal judge today will hear arguments in a suit challenging Minnesota's Next Generation Energy Act.
North Dakota is suing Minnesota over provisions in the 2007 law that set limits on new coal-fired power plants.
The law says utilities may not build new coal plants in Minnesota or import electricity from new coal plants built elsewhere unless they offset the added carbon emissions that contribute to global warming.
North Dakota says that stipulation violates the interstate commerce clause of the U.S. Constitution, and usurps the federal government's regulation of the wholesale power market.
Minnesota says the law merely limits the type of electricity that may be sold at the retail level.
North Dakota mines coal, and has several power plants that already supply Minnesota customers.
The judge is not expected to rule today.