In a hit to the Trump administration, the Supreme Court unanimously ruled Monday that cases litigating the Clean Water Act should be heard by federal district courts.

The administration had argued those cases should be heard in federal appeals courts.

The Supreme Court agreed to hear the case over an Obama-era regulation, known as the Waters of the United States (WOTUS) rule, back in January 2017, after debate as to whether the U.S. Court of Appeals or federal district courts had the authority to hear the lawsuits from industry groups and states that say the rule went too far.

Dozens of parties had filed lawsuits over the regulation in both federal appeals courts and district courts.

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Industry groups, led by the National Association of Manufacturers, argued that under the Clean Water Act, lower district courts should first hear the challenges, which can then be appealed to the Supreme Court.

The Trump administration, on the other hand, said the challenges were legally within the purview of appeals courts because the rule touched on the Environmental Protection Agency's (EPA) permitting authority.

“Today’s unanimous Supreme Court decision provides much needed clarity and affirms our longstanding position that the Clean Water Act empowers the federal district courts, not the courts of appeals, to initially review legal challenges to the Waters of the U.S. Rule,” National Mining Association President and CEO Hal Quinn said in a joint statement Monday.

“This win, coupled with the administration's actions in proposing to repeal the rule and seek input on how to properly define ‘waters of the U.S.,’ puts us one step closer to addressing this deeply problematic rule and the confusion it has created,” he said.

The case, National Association of Manufacturers v. Department of Defense, did not concern the merits of the 2015 Obama-era rule, under which the EPA and Army Corps of Engineers asserted jurisdiction over small waterways like ponds and streams.

The regulation aimed to clarify which wetlands and streams were to be given automatic protection under the law.

However, the lawsuits are nearly moot. In June, the EPA took the first formal step to uphold President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE's campaign promise to repeal and replace the 2015 regulation.

The proposal said federal officials would go back to enforcing a guidance document from 2008 when deciding whether a waterway is subject to federal oversight for pollution control purposes.

While some environmentalists are hopeful the Supreme Court ruling will leave open the door for the Clean Water rule to be put into effect while the court cases are carried out, the Trump administration expects a stay on the rule to be finalized shortly.

“The Trump administration saw this decision coming and put a plan in place to level the playing field and ensure certainty for states and regulated community. The Trump administration’s stay of the 2015 WOTUS rule will very likely be complete before any change in court jurisdiction can be finalized, or the Obama administration’s overreaching definition of WOTUS can be implemented,” EPA spokeswoman Liz Bowman told The Hill on Tuesday.

Updated Jan. 23 at 11:17 a.m.