KCP&L contends that because the dispute involves the transmission of power across state lines, the Federal Energy Regulatory Commission is in charge of setting the rates for transmitting from Mississippi. It says the Missouri Public Service Commission had no authority to intervene.

Utilities nationwide are watching the case because they have always assumed that transmission costs across state lines could be recovered from customers.

The trade group Edison Electric Institute warns in a filing to the Supreme Court that “the Missouri loophole is . uniquely positioned to spread like a virus to other states.”

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