This presentation will provide a substantive review of the Trump administration's new Navigable Waters Protection Rule, which redefines the scope of waters of the United States under federal Clean Water Act jurisdiction. We will dissect the new rule, highlight its key (and controversial) provisions, and how it impacts the NPDES permitting program. We will also look ahead to the impending legal challenges to the rule and how the rule may be vulnerable to attack, or defended, in light of prior judicial decisions.