The Seventh Circuit, in the case of State of Michigan, et al. v. US Army Corps of Engineers and the Metropolitan Water Reclamation District of Greater Chicago, once again denied a request by five states bordering on Lake Michigan seeking an injunction against the Corps and the Water Reclamation District. The Asian carp threatens to overwhelm the Great Lakes unless its migration through the Chicago Area Waterway System which connects Lake Michigan with the Mississippi River. The states appear to favor a hugely expensive and environmentally questionable project to physically separate these bodies of water to prevent the carp from entering and pillaging the Great Lakes. The court denied relief, but the opinion by Judge Wood is a masterful exposition of federal common law principles, nuisance law, and the way the 1899 River and Harbors Act is intended to work. The court declined the invitation to step into the middle of this controversy, while it acknowledges that some progress has been reported.