(CNN) A federal district court judge Thursday blocked another Trump administration effort to undermine Obamacare.

The decision hits a Labor Department rule designed to make it easier for small businesses to band together and buy health insurance in so-called association health plans -- one of the Trump administration's initiatives to weaken Obamacare by offering alternatives to the exchanges.

The order, Trump said at the time, would give "millions of Americans with Obamacare relief."

But in Thursday's decision, Judge John Bates of the US District Court in the District of Columbia disagreed, saying the goal of the association health plan, or AHP, rule was to allow participants to avoid certain Obamacare regulations.

"The final rule is clearly an end-run around the ACA," Bates wrote. "Indeed, as the President directed, and the Secretary of Labor confirmed, the final rule was designed to expand access to AHPs in order to avoid the most stringent requirements of the ACA."

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