Two federal agencies in Washington are tangled in a turf war over the regulation of commodity futures markets, quarreling over the authority to enforce rules against the trader at the center of the collapse of the hedge fund Amaranth in 2006.

The U.S. Commodity Futures Trading Commission sued Amaranth’s head energy trader, Brian Hunter, in federal district court in New York in 2007 alleging he attempted to manipulate the price of natural gas futures. The Federal Energy Regulatory Commission simultaneously brought an administrative action against Hunter, claiming that his trades affected prices in the physical natural-gas market.