MADISON, Wis. (CHANNEL 3000 / AP) -

A state appeals court says prosecutors can't change drunken driving charges once they're filed without a judge's permission.

The case stems from Oneida County prosecutors' decision to downgrade a fourth-offense felony drunken driving charge against Brian Corvino to a misdemeanor as part of a plea deal. Judge Michael Bloom refused to allow the deal, saying state law requires him to approve changes to drunken driving charges and to allow the downgrade wouldn't serve the public interest in deterring drunken driving. He ordered prosecutors to charge Corvino with a felony.

The 3rd District Court of Appeals sided with Bloom on Tuesday, ruling the judge properly refused to allow prosecutors to change the charge and had the authority to order a felony count.

Corvino's attorney didn't immediately return a voicemail.