Two environmental groups are suing the Environmental Protection Agency over protection of Minnesota waters from invasive species.
The National Wildlife Federation and the Minnesota Conservation Federation are asking a federal judge to strike down an EPA rule.
The rule says courts cannot modify EPA permits for ballast water in ships.
The two groups had asked a Minnesota court to rule that Minnesota's conditions attached to a ballast water permit were not adequate. The state court said the EPA rule made the case moot.
National Wildlife Federation attorney Neil Kagan said if they win the federal case, they will come back to state court in order to "evaluate whether Minnesota's conditions are stringent enough to prevent invasive species and protect the quality of the state's waters."
"The state court said because of this federal rule, we're not going to evaluate whether Minnesota's conditions on the EPA permit are adequate to protect state water quality," Kagan said. "We have to get that rule out of the way."
Kagan said New York is the only state with strict enough rules to protect against aquatic invasive species.