A federal judge has overturned water quality rules that were meant to protect southeastern Montana cropland from natural gas drilling but were assailed by Wyoming as a threat to energy production.

The rules covered the Tongue and Powder rivers, which flow north from the rich gas fields of northeastern Wyoming into primarily agricultural land in Montana.

Drafted by Montana and approved by the Environmental Protection Agency, the rules limited how much salty water – a byproduct of drilling – could enter the rivers. State officials said the EPA had not yet begun to enforce the rules, in part because of a pending lawsuit.
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