A federal judge late Sunday ordered that the U.S. Postal Service not implement President Donald Trump’s executive order limiting mail balloting, adding another obstacle to the administration’s effort to rewrite election rules as the Supreme Court is poised to weigh in on the matter.

The nation’s highest court already is considering the administration’s appeal of an order by U.S. District Court Judge Indira Talwani in Boston prohibiting the Postal Service from enforcing its new rule on mail voting before this year’s midterm elections.

Late Sunday, U.S. District Judge Carl J. Nichols in Washington, D.C., handed down a similar hold on the rule, which was issued Aug. 21.

“Plaintiffs have demonstrated that, absent an injunction, there is an increased risk that a significant number of otherwise appropriate absentee or mail-in ballots will ultimately not be counted in the upcoming elections,” Nichols wrote in issuing the preliminary injunction. “The public has a strong interest in ensuring that doesn’t happen.”

Nichols in May had refused to issue an injunction because he ruled the lawsuit seeking one was brought too early. That was the high court’s reasoning late last month when it lifted an earlier freeze by Talwani. But because the administration had just issued its rule to move ahead with Trump’s plan, the plaintiffs in Boston and Washington, D.C., refiled their lawsuits.

Talwani was nominated by former President Barack Obama and Nichols was nominated by Trump.

The new Postal Service regulations stem from an executive order Trump issued earlier this year. Election officials say it would be impossible to implement the changes this close to a general election.