Georgia Attorney General Sam Olens blasted the Obama Administration in a letter Thursday to state lawmakers, saying proposed new rules about which bodies of water federal officials oversee under the Clean Water Act “would drastically and unlawfully expand federal control over Georgia’s water resources.”

Olens added that he will monitor how the administration handles the proposal “to be sure that Georgia is involved in related legal actions where necessary and appropriate.”

The letter came as lawmakers held a hearing at the state Capitol to better understand what impact the proposed rules would have on the state, where officials estimate agriculture has a $77 billion impact. Georgia Agriculture Commissioner Gary Black has already called the proposal “a serious threat…to the rights of farmers and American citizens alike.”

The U.S. Environmental Protection Agency has said the new rules are needed to clarify its jurisdiction, following Supreme Court rulings in 2001 and 2006 over how it determined which waters were protected under federal law.

Both federal officials and environmentalists say the proposal does not add new protection to waters that have not historically been protected by the Clean Water Act. Opponents say the rules are a power grab that could stifle economic growth and intrude on property owners’ rights.

States have until Oct. 20 to submit comments to the EPA about the proposal.