The National Wildlife Federation is suing the U.S. Environmental Protection Agency over the agency's new ballast water discharge permit.
The EPA will require ships entering the Great Lakes and other U.S. waters to get a permit, before dumping their ballast water.
But the environmental group says the permit is weak and won't keep new non-native species from getting into the lakes.
Marc Smith is senior policy manager for the environmental group.
He says prevention is the only way to keep new species from joining other invasives, like zebra mussels.
"You know, by the time we discovered them, we found them in such population and high numbers that it was irreversible."
The U.S. EPA referred questions on the lawsuit to the U.S. Justice Department, which declined to comment.
