Halting the Invasion in the Chesapeake Bay: Preventing Aquatic Invasive Species Introduction through Regional Cooperation (Dec 2007) Environmental Law Institute. A report by attorney Read D. Porter that examines coordination on aquatic invasive species prevention among the Chesapeake Baystates. The report focuses on prevention-related legal authorities in Virginia, Maryland, and Pennsylvania in particular, and recommends actions to improve regional cooperation both within the existing regulatory frameworks and through potential amendments to state laws and regulations to enhance prevention.