The decision means the seat will remain empty until the lawsuit and possible appeals in state court are complete. Republican Norm Coleman's lawsuit challenging Franken's recount lead is at the end of its sixth week, and both sides expect it to last at least a few more weeks.

After a state board certified recount results showed Franken 225 votes ahead, he sued to force Gov. Tim Pawlenty and Secretary of State Mark Ritchie to sign an election certificate. Franken argued that federal law stipulates each state will have two senators when the Senate convenes, and that law trumped a state law that blocks such certificates while lawsuits are pending.

But the state Supreme Court disagreed. In their ruling Friday, the justices said states aren't required to issue such certificates by the date that Congress convenes.

The justices wrote in their unsigned opinion that "if the Senate believes delay in seating the second Senator from Minnesota adversely affects the Senate, it has the authority to remedy the situation and needs no certificate of election from the Governor to do so."