On June 21, 2012, the Coast Guard’s final rule on vessel ballast water management, first published on March 23, 2012 in the Federal Register, became effective. The rule is the latest chapter in efforts by the U.S. Government to address the problem of invasive species being deposited in U.S. waters in ballast water. Authority for the rule stems from the National Invasive Species Act of 1996 in a rulemaking which commenced on August 28, 2009. The rule establishes, for the first time, a discharge standard for living organisms which ballast water management systems must be able to satisfy (a phase-one standard). The timing of the application of the phase-one standard to particular vessels depends on their construction date. The rule also anticipates making that standard more stringent in the future (a phase-two standard). Ballast water exchange remains an approved compliance method but will be phased out. The rule also set forth a process by which the Coast Guard approves ballast water management systems for use in the future. The rule is separate and apart from the Environmental Protection Agency’s ongoing Vessel General Permit process, which also covers ballast water discharges.