LANSING, Mich. (Michigan News Source) — Michigan Attorney General Dana Nessel is back in court over what could be lurking in the bottom of cargo ships.

Nessel has asked a federal appeals court to block the Environmental Protection Agency’s (EPA) new ballast water rules, arguing they weaken long-standing protections designed to keep invasive species out of the Great Lakes.

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The lawsuit challenges standards finalized in 2024 that replaced Michigan’s stricter ballast regulations with a single national framework. Nessel says the move violates the 2018 Vessel Incidental Discharge Act and opens the door to new ecological threats.

Ballast water—used to stabilize large vessels—is a well-documented pathway for invasive species. Zebra mussels, introduced decades ago through ship discharges, still cost the Great Lakes region an estimated $200 million annually.

Nessel also cited the recent detection of golden mussels, a fast-spreading invasive species, at a California port as a warning sign of what could come next.

In short, the EPA says its rules streamline oversight. Nessel says the Great Lakes can’t afford the experiment.