Fifth-generation farmer Kenny Watkins ran afoul of the U.S. clean-water police in 2009. His infraction: Planting hay in a pasture.

The U.S. Army Corps of Engineers ordered Watkins to stop cultivating a 160-acre (65-hectare) tract in central California because he might destroy seasonal ponds and harm the San Joaquin River. Watkins has defied the decision and the federal government’s control over what he can grow on his farm.

His battle is cited by agriculture groups as they try to fend off a proposal by the Corps and the Environmental Protection Agency to enlarge the U.S. role in guarding waterways against contamination. The two agencies are reviewing a plan that would require permits under the Clean Water Act for work on wetlands or small channels that are usually dry. They say they’re clarifying authority they already have and critics say it’s a power grab.