A federal judge in Washington, D.C., has struck down a proposed rule by the Trump administration intended to dismantle part of the Affordable Care Act, or Obamacare, by allowing small businesses and self-employed individuals to collectively participate in a health care plan.

The rule was promulgated by the U.S. Department of Labor last year as a way to save those groups money on health care by participating in so-called association health plans, which allow employers to provide health coverage with fewer benefits than mandated under Obamacare.