Water quality trading presents an exciting and innovative opportunity to achieve clean water improvements in an environmentally responsible and cost-effective way. This is particularly true for the Chesapeake Bay watershed and others that are impaired by excess nutrients such as nitrogen and phosphorus. Nutrient trading programs, especially those between point and nonpoint dischargers, hold tremendous promise for achieving water quality improvements in the Bay -- so much so that trading was incorporated as part of the EPA's final 2010 total maximum daily load (TMDL) for the Chesapeake Bay watershed. Unfortunately, the trading component of the Bay TMDL has come under legal attack, and NACWA is moving aggressively to defend water quality trading in court. In early October , several environmental activist groups filed a misguided and misinformed lawsuit against EPA challenging the trading program included in the final Bay TMDL as illegal under the Clean Water Act (CWA). The lawsuit in particular calls out trading programs between point and nonpoint sources and -- perhaps most concerning -- could invalidate not just trading within the Chesapeake Bay but all water quality trading programs nationwide.