MINNEAPOLIS (AP) -- The Minnesota Supreme Court has reversed an appeals court's rejection of a critical air emissions permit for the planned PolyMet copper-nickel mine and sent the case back for further proceedings.

The court ruled Wednesday that the Minnesota Pollution Control Agency was not required under federal law to investigate allegations of ``sham permitting.''

The high court overturned a decision by the Minnesota Court of Appeals last March to send the air permit for the $1 billion mine back to the regulators for further review.

PolyMet would be Minnesota's first copper-nickel mine.

The appeals court will now consider other allegations.

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