A federal court Monday rejected central pieces of the Environmental Protection Agency’s (EPA) regulations to reduce the spread of invasive species through ship ballast water.

The United States Court of Appeals for the Second Circuit, based in New York City, ruled 3-0 that the EPA’s decision to adopt an international standard for the technology to filter ballast water was “arbitrary and capricious,” among other provisions in the 2013 regulation.

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Ballast, which is used to stabilize and balance ships, is a key culprit of the spread of invasive species such as the zebra mussel. Ships take ballast water from one part of the world to others, running the risk of bringing non-native species that could harm ecosystems.

The decision is a major win for a coalition of environmental groups that had sued, saying the EPA did not adequately explain why it couldn’t go further in mandating technology and practices to reduce the movement of organisms.

The court is asking the EPA to reconsider its decisions regarding technology, its exemption for certain older ships and other parts of the rule, but the regulation will stay in place while the agency undertakes the process.

The National Wildlife Federation, one of the groups that had brought the litigation, cheered its outcome.

“This is a huge win for our environment, economy, fish, wildlife, communities and businesses,” said Marc Smith, the group’s policy director.

“The court, in no uncertain terms, has told the federal government that it needs to uphold its responsibility under the Clean Water Act to protect our drinking water, jobs and way of life,” he said.