Transport of invasive species in the ballast water of ships threatens marine ecosystems globally. Policy in the United States to control unwanted introductions began over 25 years ago with the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990, later the National Invasive Species Act of 1996, and has now expanded to include oversight from multiple federal agencies and state governments. Simultaneously, the International Maritime Organization has directed attempts to regulate ballast water on the global scale. Management priorities have shifted from mid-ocean ballast water exchange toward quantitative standards of allowable organism density upon discharge. However, critical management exemptions are resulting in unnecessary risk, particularly in ports that receive primarily coastal vessel traffic. For example, in the United States, exemptions for crude oil tankers engaged in coastwise trade have existed since 1996. When management and recordkeeping requirements went into place for these vessels in 2008 the result was an apparent 440% increase in ballast water discharge to Alaska in the following year. Our review of ballast water management policy suggests that a precautionary approach to exemptions coupled with scenario-specific risk assessments may reduce risk of invasion in ecosystems, like those of coastal Alaska, that are susceptible to further, or new, invasions.